A TEST OF THE VALIDITY OF MORPHOMETRIC ANALYSIS IN ...
A TEST OF THE VALIDITY OF MORPHOMETRIC ANALYSIS IN ...
A TEST OF THE VALIDITY OF MORPHOMETRIC ANALYSIS IN ...
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A <strong>TEST</strong> <strong>OF</strong> <strong>THE</strong> <strong>VALIDITY</strong> <strong>OF</strong> <strong>MORPHOMETRIC</strong> <strong>ANALYSIS</strong> <strong>IN</strong><br />
DETERM<strong>IN</strong><strong>IN</strong>G TECTONIC ACTIVITY FROM ASTER DERIVED DEMs<br />
<strong>IN</strong> <strong>THE</strong> JORDAN-DEAD SEA TRANSFORM ZONE
A <strong>TEST</strong> <strong>OF</strong> <strong>THE</strong> <strong>VALIDITY</strong> <strong>OF</strong> <strong>MORPHOMETRIC</strong> <strong>ANALYSIS</strong> <strong>IN</strong><br />
DETERM<strong>IN</strong><strong>IN</strong>G TECTONIC ACTIVITY FROM ASTER DERIVED DEMs<br />
<strong>IN</strong> <strong>THE</strong> JORDAN-DEAD SEA TRANSFORM ZONE<br />
A dissertation submitted in partial fulfillment<br />
of the requirements for the degree of<br />
Doctor of Philosophy<br />
By<br />
Husam Abbas Ata, B. A., M. A.<br />
Yarmouk University, 1995<br />
Yarmouk University, 1998<br />
May 2008<br />
University of Arkansas
ABSTRACT<br />
The Jordan-Dead Sea Transform (JDTZ) is an active tectonic zone which is<br />
located between the Dead Sea in the north and the Gulf of Aqaba in the south and extends<br />
approximately 245 km. The JDTZ has a complicated geomorphological setting and varied<br />
geology and it contains a number of active faults that were associated with several<br />
significant destructive earthquakes in the region. This research was initiated to develop a<br />
morphometric digital approach to examine the mountain front geomorphic form along the<br />
Jordan-Dead Sea Transform Zone to obtain intensive analysis of its potential as an<br />
indicator of seismic activity.<br />
Four ASTER scenes were used as a visual digital data reference to locate<br />
geomorphic forms along the mountain fronts in the study area. Using the ASTER<br />
generated DEMs of ±10m vertical accuracy as a base elevation reference layer, several<br />
significant mountain fronts and valley profiles were digitized using GIS technology to<br />
precisely determine their morphometric indices. The mountain front sinuosity (S mf ) and<br />
the ratio of valley floor width to valley height (V f ) morphometric indices were utilized to<br />
analyze the several mountain fronts and valleys in the JDTZ to determine their tectonic<br />
activity.<br />
The final morphometric analysis of S mf results indicated two major tectonic<br />
activity classes within the JDTZ. The active tectonic class 1 values range from 1.00 to<br />
1.30 while the moderate to less active class 2 values are >1.30. On the other hand, the V f<br />
analysis results suggest the existence of three tectonic activity classes. The active tectonic<br />
class 1 values range from ≤ 0.09 to 0.50, the moderate to less active class 2 values range<br />
from 0.51 to 1.88, and the less active (inactive) class 3 values are >1.88.
This dissertation is approved for<br />
Recommendation to the<br />
Graduate Council<br />
Dissertation Director:<br />
_________________________________________________________<br />
John C. Dixon, PhD<br />
Dissertation Committee:<br />
_________________________________________________________<br />
Jackson D. Cothren, PhD<br />
_________________________________________________________<br />
Pamela E. Jansma, PhD<br />
__________________________________________________________<br />
Thomas R. Paradise, PhD
DISSERTATION DUPLICATION RELEASE<br />
I hereby authorize the University of Arkansas Libraries to duplicate this dissertation<br />
when needed for research and/or scholarship.<br />
Agreed _____________________________________<br />
Refused ____________________________________
ACKNOWLEDGEMENTS<br />
“When I look back upon my early days, I am stirred by the thought of the number of<br />
people I have to thank for what they gave me or for what they were to me. . . . . I think we<br />
all live spiritually, by what others have given us in the significant hours of our lives” -<br />
Albert Schweitzer (1875-1965), a German philosopher, physician, musician, theologian,<br />
and the 1952 Nobel Peace Prize winner.<br />
From the formative stages of this dissertation, to the final draft, I owe an immense<br />
debt of gratitude to my supervisor, Dr. John C. Dixon, for his constant academic support<br />
and his words of encouragement and help throughout my graduate study and research. I<br />
would like to express thanks to Dr. Jackson Cothren, who never gave up on me. He was<br />
always interested in the work and helped me find answers regardless of the research<br />
challenges. I also want to thank Dr. Pamela Jansma and Dr. Thomas Paradise for their<br />
scholastic assistance and contribution to my research. Put these scholars together and it is<br />
the dynamic committee that words can never adequately describe. I would also like to<br />
extend my appreciation to the King Fahd Center for Middle East and Islamic Studies for<br />
the financial support they offered to conduct and maintain my graduate research.<br />
Second, I would like to acknowledge all the professors, technicians, and staff of<br />
the Center for Advanced Spatial Technologies (CAST) who were always willing to<br />
answer questions, and helped me locate valuable information. In addition, I would like to<br />
thank the environmental dynamics’ professors who taught and enlighten me. They were<br />
interested as I in seeing this study done. Moreover, I would like to thank the geosciences<br />
department’s staff and my fellow graduate students for their assistance and support.<br />
Finally, I would like to thank my faithful wife Nadia Khrais, without her support<br />
and steady encouragement this work would never have been completed. I also want to<br />
thank my parents, sisters, precious son, and family who offered me unconditional love,<br />
support, encouragement and surrounded me with their blessing and prayers.<br />
v
DEDICATION<br />
To my father and mother,<br />
To my two sisters, and<br />
To my wife and son,<br />
With love and gratitude<br />
vi
TABLE <strong>OF</strong> CONTENTS<br />
Title<br />
Page<br />
Abstract..………………………………………………………..………………… ii<br />
Acknowledgments...……………………………………………………………… v<br />
Dedication………..…………………….…………………………………………. vi<br />
Table of Contents………………………..…………………...…………………… vii<br />
List of Figures…..………..……………..………………………………………… x<br />
List of Tables…..…………………….…………………………………………… xvi<br />
List of Abbreviations – Keywords……………...………………………………… xvii<br />
1. Chapter One: Introduction…...………………………………………………… 1<br />
1.1. Research objectives…..……………………………………………………… 1<br />
1.2. Research problem…...……………………………………………………….. 1<br />
1.3. Justification of the Study..…………………………………………………… 4<br />
1.4. The Jordan-Dead Sea Transform Zone characteristics..…………………….. 6<br />
1.4.1. Geomorphology of the JDTZ.…………………….…………………….. 6<br />
1.4.1.1. Rifting Process and Extensional Tectonics..……………………… 16<br />
1.4.2. Structure and Geology of the JDTZ…..………………………………… 20<br />
1.4.2.1. Structure…..………………………………………………………. 20<br />
1.4.2.1.a. Wadi Araba…...…………………………………………… 20<br />
1.4.2.1.b. The Dead Sea…...………………………………………… 21<br />
1.4.2.2. Geology…...………………………………………………………. 23<br />
1.4.2.2.a. The Aqaba Complex...…………………………………….. 25<br />
1.4.2.2.b. The Araba Complex...…………………………………….. 25<br />
1.4.2.2.c. The Dead Sea..……………………………………………. 26<br />
1.4.3. Seismicity of the JDTZ..……………………………………………...… 30<br />
1.4.3.1. Regional tectonics of Jordan and its vicinity..………………….… 30<br />
1.4.3.2. Seismotectonic maps of Jordan..….………………………………. 33<br />
1.4.3.3. Seismic maps of the JDTZ..…….……………………………….... 37<br />
1.4.3.4. Jordan/JDTZ earthquakes data..……………………………...…… 42<br />
2. Chapter Two: Literature Review..…………………………………………...… 46<br />
vii
2.1. Introduction..………………………………………………………………… 46<br />
2.1.1. Morphometric analysis in geomorphology…......………………………. 46<br />
2.1.2. Remote sensing and GIS uses in geomorphology..……………………... 48<br />
2.2. Morphometric analysis approach..……………………………………...…… 50<br />
2.3. Geomorphic indices of active tectonics..………………………………….… 51<br />
2.3.1. The Hypsometric Curve and Hypsometric Integral (H i )..….…………… 52<br />
2.3.2. Drainage Basin Asymmetry (AF)..…………………………………...… 54<br />
2.3.3. Stream Length-Gradient Index (SL)..…………………………...……… 57<br />
2.3.4. Triangular Facets Index (Pf)..…………………………………...……… 59<br />
2.3.5. Mountain front sinuosity (S mf )..………………………………………… 62<br />
2.3.5.1. Choosing mountain fronts……………………..….….…………… 64<br />
2.3.6. Valley floor width to valley height ratio (V f )...……..……………...…… 65<br />
2.3.6.1. Choosing valley profiles..………………………………………… 66<br />
2.4. Satellite imagery and digital elevation models.…..…………..……………… 67<br />
2.4.1. Digital Elevation Model………...………………………………….…… 68<br />
2.5. Advanced Spaceborne Thermal Emission and Reflection Radiometer<br />
Satellite..……………………………………………………………………... 72<br />
2.5.1. ASTER data types..……………………………………………………... 73<br />
2.6. Previous studies in morphometric analysis….………………...…………..… 74<br />
2.7. Summary..…………………………………………………………………… 82<br />
3. Chapter Three: Materials and Methods..…………………..…………………... 84<br />
3.1. Introduction..………………………………………………………………… 84<br />
3.2. The digital morphometric approach..……………………...………………… 84<br />
3.2.1. Choosing mountain fronts..………………………………………...…… 85<br />
3.2.2. Choosing valley profiles..………………………………….…………… 85<br />
3.3. ASTER Stereo capability..……………………………………...…………… 85<br />
3.4. Obtaining ASTER imagery data..……………….…………………………… 87<br />
3.5. Viewing ASTER data in PCI Geomatica..……………………………...…… 89<br />
3.6. Generating ASTER DEMs…..………………………………….…………… 91<br />
3.6.1. Generating and extracting DEMs from ASTER data…..………..……… 92<br />
3.6.1.1. PCI Geomatica software……..…………………………………… 92<br />
viii
3.6.1.2. DEMs extraction process…..………………………………...…… 97<br />
3.6.1.3. The math model….……………………………………..………… 100<br />
3.6.1.4. DEMs editing process…..………………………………………… 118<br />
3.6.1.5. Transferring ASTER DEM to GIS environment…..……...……… 127<br />
3.7. Obtaining Landsat 7 ETM+ imagery…..………...……………………..…… 130<br />
3.7.1. Creating ASTER and Landsat composite images…..…………………... 130<br />
3.8. Obtaining vector data……..…………………………………………….…… 133<br />
3.8.1. Converting Interchange files to Shapefiles in ArcToolbox…...………… 134<br />
3.8.2. Digitizing vector data…...………………………………………….…… 137<br />
3.8.3. Digitizing mountain fronts and measuring sinuosity…..……..………… 138<br />
3.8.4. Digitizing valley profiles and measuring elevations and valleys’ widths. 153<br />
4. Chapter Four: Results and Discussion…..……………..……………………… 162<br />
4.1. Introduction…..……………………………………………...……….……… 162<br />
4.2. The tectonic morphometric analysis…...…………………..………………… 163<br />
4.2.1. Mountain front sinuosity results……...……………….………………… 166<br />
4.2.2. The ratio of valley floor width to valley height results…..……...……… 166<br />
4.3. Seismic activity at mountain fronts…..……………………………………… 168<br />
4.4. The accuracy of ASTER DEM data.….………………...…………………… 172<br />
4.5. ASTER DEM error test…..…………………………………………..……… 175<br />
4.6. Final results and tectonic activity classes…..………...……………………… 190<br />
5. Chapter Five: Conclusion…..……………………………...……...…………… 194<br />
5.1. Conclusion…...………………………………………………………………. 194<br />
5.2. Limitation of the Study…..…….……………………………..……………… 196<br />
5.3. Future directions/remarks…..…………………………...…………………… 196<br />
Bibleography……………………………………………………………………… 198<br />
Appendix A…..…………………………………………………………....……… 216<br />
ix
LIST <strong>OF</strong> FIGURES<br />
Figure<br />
Page<br />
1.1: Earthquakes in the Jordan-Dead Sea Transform and adjacent areas, 1900-<br />
1980……………………………………………………………………….…... 2<br />
1.2: Jordan-Dead Sea Transform Zone (JDTZ) dimensions.….….……………... 7<br />
1.3: East African Rift System …………………...………………...….................. 8<br />
1.4: Tectonic setting of the Middle East......…………………...…………...…… 9<br />
1.5: Wadi Araba Valley location map along the Jordan-Dead Sea Transform<br />
fault system………...………………...…………………...…………………... 10<br />
1.6: Block diagram along the central part of the JDTZ illustrating the tectonic<br />
style and the continuous rise of the graben floor.…………………...………... 12<br />
1.7: The Aqaba-Dead Sea-Jordan subgraben system….………………................ 13<br />
1.8: A block diagram showing the strike-slip geometry along the JDTZ<br />
representing the en echelon fault system.………………..………...…………. 15<br />
1.9: The seven pillars of Wisdom of southern Jordan………..………………….. 16<br />
1.10: The East Africa Rift Valleys as an example of the rifting process......……. 16<br />
1.11: Rift structure.…...………….…………………...………………..…............ 17<br />
1.12 Normal fault system..……………………………………………….……… 18<br />
1.13 (a) Symmetric horst and graben system (b) Half-graben system above the<br />
subhorizontal fault detachment.…………………...…….…………….…...…. 19<br />
1.14 Alluvial fans (bajadas) at the southern end along the eastern side of Wadi<br />
Araba…………………...…………………...………………………................ 20<br />
1.15 Dead Sea location map showing the two basins.………………..……......... 23<br />
1.16 Jordan-Dead Sea Fault simplified geological cross-section.……..……..….. 24<br />
1.17: A simplified geological cross section across the southern section of the<br />
Jordan-Dead Sea Transform.…………………...…………………................... 25<br />
1.18: Rock types and the locations of all mountain fronts in the JDTZ.…...……. 29<br />
1.19: Bouguer gravity anomaly map of Dead Sea transform, Jordan and Israel… 34<br />
1.20: (A) The thirteen seismic zones and (B) major faults within the thirteen<br />
seismic zones in Jordan and its vicinity………………..……………...…….... 35<br />
x
1.21: The Dead Sea fault and the adjacent branching faults…..………………… 37<br />
1.22: Seismic map of the Middle East 1900 – 1983…..………………………..... 38<br />
1.23: Seismic zones and active faults of Jordan and surrounding countries.......... 41<br />
1.24: Major earthquake events on Jordan, 19A.D. – August 1983….…………... 44<br />
1.25: Major earthquake events on Jordan, September 1983 – 2005…………….. 45<br />
2.1: Hypsometric curve derivation from drainage basin……….………………... 54<br />
2.2: Block diagram shows the effect of an asymmetry factor with a left side tilt<br />
on tributaries lengths…..…………………...…….……………........................ 55<br />
2.3: An example of calculating a drainage-basin transverse topographic<br />
asymmetry vector for a single stream segment.…………………………..…... 56<br />
2.4: Map showing the Stream Length-Gradient Index (SL)…………..…….….... 57<br />
2.5: Diagram shows the process of calculating the Stream Length-Gradient<br />
Index (SL).…………………...…………………...…………………............... 59<br />
2.6: Rapid and slow block uplift produces………..………...………………….... 60<br />
2.7: Circular and elongated basins.…………………...…..……………………... 61<br />
2.8: Location of older and younger triangular facets to mountain fronts……..…. 62<br />
2.9: Calculating mountain front sinuosity (S mf ) index…………………………... 63<br />
2.10: Mountain front sinuosity (S mf ) index...……………...…………...………... 63<br />
2.11: Calculating valley floor width to height ratio (V f )..………………..….…... 66<br />
2.12: Valley floor width to height ratio (V f ).…………………...………..……… 66<br />
2.13: The Aqaba 1:50,000-scale topographic map with 20m intervals..….…….. 70<br />
2.14: Flat map shows ASTER DEM global coverage of January 31,<br />
2004…………………………………………………………………..……….. 73<br />
2.15: Data structure of ASTER Level-1B granule…………….…………............ 75<br />
3.1: Simplified diagram of imaging geometry and data acquisition timing for<br />
ASTER along-track stereo image.…………………...………………….......... 86<br />
3.2: Simplified diagram of the imaging geometry for ASTER along-track stereo<br />
image “stereo configuration”...……………...……….………………….......... 87<br />
3.3: The USGS global visualization viewer showing ASTER scenes of Jordan... 88<br />
3.4: Focus is the first icon on the Geomatica Toolbar.………………..….……... 90<br />
3.5: Selecting ASTER VNIR sensor images.……………………...…...………... 90<br />
xi
3.6: Import File window.…………………………………..…………...………... 90<br />
3.7: ASTER 3-2-1 composite image of Aqaba.…………………………..……... 91<br />
3.8: Comparing raw images to epipolar images.…….…………..…………..…... 93<br />
3.9: Measuring height from ASTER stereopair parallax difference..……..…….. 95<br />
3.10: Summary of a standard ASTER DEM product generation process.…...….. 97<br />
3.11: OrthoEngine on the Geomatica Toolbar…………....…………….…..….... 99<br />
3.12: Opening new project from the processing step drop-down menu …...……. 100<br />
3.13: Reading satellite data from hard drive…...…………………………….….. 100<br />
3.14: Project Information window...…………………...………………………... 101<br />
3. 15: Setting project projection to UTM………………………………………... 101<br />
3.16: Setting the UTM zones……….…………………..........…………………... 102<br />
3.17: Setting the UTM rows……………………...…………….………………... 102<br />
3.18: Setting Earth Model (Ellipsoid)...………………...…...…………………... 102<br />
3.19: Setting GCPs to match the output file projection………………………….. 102<br />
3.20: Reading row ASTER data HDF files from the hard drive……………...…. 103<br />
3.21: Importing GCPs from file…………………………………...…………..… 104<br />
3.22: loading the 121 already available GCPs from image 3N file…………….... 104<br />
3.23: Dead Sea band 3N GCPs……………………...……………………….…... 105<br />
3.24: Dead Sea band 3B GCPs……………………...…………………….……... 105<br />
3.25: The image layout of bands 3N and 3B showing the location of all 121<br />
GCPs in the Dead Sea ASTER image..…………………...…………………... 105<br />
3.26: Start the Collect Ground Control Points and Tie Points manually function. 106<br />
3.27: An image show how two images connect through a tie point.…...…...…… 106<br />
3.28: Collecting tie points manually from both images…......…………………... 107<br />
3.29: Opening both uncorrected 3N and 3B images to manually collect tie<br />
points.…………………...………………………………...…………………... 108<br />
3.30: Collecting tie point window for Aqaba image 3N.……………..…......…... 108<br />
3.31: Automatically Collect tie points.……………..…….....………….………... 109<br />
3.32: Automatically Collect tie points uniformly over an entire image….…..….. 110<br />
3.33: Band 3N tie points (North Araba).……………………..………………….. 111<br />
3.34: Band 3B tie points (North Araba).……………...……...………………….. 111<br />
xii
3.35: Displaying overall image layout from both images.…...…...……………... 111<br />
3.36: Image layout of both bands 3N and 3B for the North Araba scene.…...….. 112<br />
3.37: Running Model Calculation to perform bundle adjustment.…..………….. 112<br />
3.38: Creating a DEM from stereo pairs using image correlation.………..…….. 113<br />
3.39: Create Epipolar image icon.…………………...……………….…...……... 114<br />
3.40: Generate Epipolar images window.…………………...…………..………. 114<br />
3.41: Extract DEM Automatically icon.…………………...…………..………... 115<br />
3.42: Automatic DEM extraction window showing all used options for Aqaba... 116<br />
3.43: The multi-resolution image pyramids.…………………….......…...……… 118<br />
3.44: The Dead Sea generated DEM.…………………...…………...…………... 119<br />
3.45: North Araba generated DEM.…………………...……….....……………... 119<br />
3.46: South Araba generated DEM.…………………...….…..……..…………... 120<br />
3.47: Aqaba generated DEM.…………………...………………...…..………… 120<br />
3.48: General view of the clipped GTOPO30 DEM of the Middle East showing<br />
the JDTZ.…………………...…………………...……………………..……... 122<br />
3.49: The XPace Tool……..…………………………………………………….. 124<br />
3.50: The Dead Sea final DEM.…………………...………………...…………... 127<br />
3.51: North Araba final DEM.…………………...……………….....…………... 127<br />
3.52: South Araba final DEM.…………………...………………..……...……... 127<br />
3.53: Aqaba final DEM.…………………...…………………...…...…………… 127<br />
3.54: Portion of the North Araba converted GRID file format to ASCII format... 129<br />
3.55: The converted North Araba DEM using ArcGIS ASCII to Raster<br />
command line.…………………...………..……………...………………….... 129<br />
3.56: Import from Interchange file window in ArcToolbox ………..…………... 134<br />
3.57: The Coverage to Shapefile tool in ArcToolbox…………………..……….. 135<br />
3.58: The Coverage to Shapefile tool window in ArcToolbox...………...……… 135<br />
3.59: The Define Projection Wizard in ArcToolbox………………………...…... 136<br />
3.60: The Define Projection Wizard window under Projections in ArcToolbox... 137<br />
3.61: Map shows the Dead Sea shoreline and Jordan borders before and after<br />
editing.…………………………………….…….…………………………….. 138<br />
3.62: The Gulf of Aqaba generated DEM and shaded relief….……………….… 139<br />
xiii
3.63: Dead Sea ASTER color composite 3-2-1………………………………….. 140<br />
3.64: Dead Sea ASTER-derived DEM…………………………………………... 141<br />
3.65: Dead Sea shaded relief…………………………………………………….. 142<br />
3.66: North Araba ASTER color composite 3-2-1………………………………. 143<br />
3.67: North Araba ASTER-derived DEM……………………………………….. 144<br />
3.68: North Araba shaded relief…………………………………………………. 145<br />
3.69: South Araba ASTER color composite 3-2-1………………………………. 146<br />
3.70: South Araba ASTER-derived DEM……………………………………….. 147<br />
3.71: North Araba shaded relief…………………………………………………. 148<br />
3.72: Aqaba ASTER color composite 3-2-1…………………………………….. 149<br />
3.73: Aqaba ASTER-derived DEM……………………………………………... 150<br />
3.74: Aqaba shaded relief………………………………………….…………….. 151<br />
3.75: An overall map of the mountain fronts and valley profiles…………….…. 152<br />
3.76: Calculating the V f value for valley profile #11 in the Dead Sea area……... 155<br />
3.77: The difference between the 2D image and the actual 3D topography of a<br />
given surface………………...…………..…...………….……………………. 156<br />
3.78: Collecting elevations from DEM as shapefile passes through raster<br />
horizontally, diagonally, and vertically.…………………….………………… 157<br />
3.79: Converting Aqaba 3D feature to points using XTools Pro...…………..….. 158<br />
3.80: General view from the Dead Sea area……………………………………... 160<br />
3.81: Collecting elevation data from profile #11 in the Dead Sea area...……..… 161<br />
4.1: Valley profile display of a V-shaped valley in South Araba and a U-shaped<br />
valley in the Dead Sea area……….…………………….……………….……. 162<br />
4.2: The tectonic activity classes of the S mf and V f indices results…………….... 165<br />
4.3: Network of earthquakes-mountain fronts’ relationship on the JDTZ<br />
showing earthquake events of M L 4 to 6 and tectonic zones, 19A.D. to<br />
August 1983…………………………………………………………………... 170<br />
4.4: Network of earthquakes-mountain fronts’ relationship on the JDTZ<br />
showing earthquake events of M L 4 to 6 and tectonic zones, September 1983<br />
to 2005……………………………………………………………………...…. 171<br />
xiv
4.5: The relationship between the ground coordinate system and the image<br />
coordinate system.………….……………...……….………………….……… 173<br />
4.6: The tectonic activity classes of all S mf and V f based on V f +σ Vf results….….. 189<br />
4.7: The active tectonic classes of the northern and southern regions of the<br />
JDTZ showing all S mf and V f +σ Vf results..………….………...……....……… 193<br />
xv
LIST <strong>OF</strong> TABLES<br />
Table<br />
Page<br />
1.1: Concise description of the mountain fronts rock types within the JDTZ...… 28<br />
2.1: The S mf and V f indices ranges of selected literature...……………………… 83<br />
3.1: ASTER scenes selected to cover the JDTZ study area...…………………… 89<br />
3.2: Specification for standard ASTER DEM products…………….…………… 96<br />
3.3: Number and type of tie points in each DEM coverage area...……………… 110<br />
3.4: Options used for all DEMs extraction processes within the study area…….. 115<br />
3.5: Overall number of digitized fronts in the JDTZ………...……………...…… 140<br />
3.6: Digitized valley profiles number and their distances upstream from<br />
mountain fronts in the JDTZ………………………………..………………… 154<br />
4.1: Brief results of all mountain fronts sinuosity (S mf ) and valleys floor width<br />
to valleys height ratio (V f ) analyses.………………………………..………… 164<br />
4.2: The percentage of the U- to V-shaped valley profiles in the JDTZ……….... 167<br />
4.3: MATLAB command lines……………………………………………...…… 183<br />
4.4: Dead Sea final σ Vf results and V f tectonic classes.....…………..…………… 184<br />
4.5: North Araba final σ Vf results and V f tectonic classes…..……..…………..… 185<br />
4.6: South Araba final σ Vf results and V f tectonic classes………….…….……… 186<br />
4.7: Aqaba final σ Vf results and V f tectonic classes...………………....………… 187<br />
4.8: Percentages change of all valleys tectonic classes after applying the ± σ Vf<br />
values.………………………………………………………………………… 191<br />
4.9: Final S mf and V f tectonic activity classes…………………………………… 192<br />
A.1: The Dead Sea S mf and V f results..…………………………..……………… 216<br />
A.2: The North Araba S mf and V f results..…………………….………………… 217<br />
A.3: The combined Dead Sea and North Araba S mf and V f results....…………… 218<br />
A.4: The South Araba S mf ) and V f results……………………………..………… 219<br />
A.5: The Aqaba S mf and V f results...……………..……………………………… 220<br />
xvi
LIST <strong>OF</strong> ABBREVIATIONS<br />
2D<br />
3D<br />
ASTER<br />
DCW<br />
DED<br />
DEMs<br />
DLG<br />
DTD<br />
DTM<br />
EOS<br />
ETM+<br />
GCPs<br />
GIS<br />
GPS<br />
JDT<br />
JDTZ<br />
JSO<br />
RMSE<br />
S mf<br />
TPs<br />
USGS<br />
UTM<br />
V f<br />
WGS<br />
Two Dimensional<br />
Three Dimensional<br />
Advanced Spaceborne Thermal Emission and Reflection Radiometer<br />
Digital Chart of the World<br />
Digital Elevation Data<br />
Digital Elevation Models<br />
Digital Line Graph<br />
Digital Terrain Data<br />
Digital Terrain Model<br />
Earth Observing System<br />
Enhanced Thematic Mapper Plus<br />
Ground Control Points<br />
Geographic Information Systems<br />
Global Positioning System<br />
Jordan-Dead Sea Transform<br />
Jordan-Dead Sea Transform Zone<br />
Jordan Seismology Observatory<br />
Root Mean Square Error<br />
Mountain Front Sinuosity<br />
Tie Points<br />
The United States Geological Survey<br />
Universal Transverse Mercator<br />
Valley Floor Width to Valley Height Ratio<br />
World Geodetic System<br />
KEYWORDS: ASTER imagery, digital elevation model, geographic information<br />
systems, geomorphic indices, geomorphic analysis, Jordan, Jordan-Dead Sea<br />
Transform Zone (JDTZ), morphometric analysis, mountain front sinuosity, satellite<br />
remote sensing, tectonic geomorphology, valley floor width to valley height ratio.<br />
xvii
1. Chapter One: Introduction<br />
1.1. Research objectives<br />
The objective of this research is to develop a digital remotely sensed approach to<br />
characterize mountain front geomorphic form along the Jordan-Dead Sea Transform<br />
Zone (JDTZ) to assess the current degree of tectonic activity and achieve detailed<br />
analysis of the mountain front’s potential as an indicator of seismic activity.<br />
1.2. Research problem<br />
The relationship between earthquakes and faulting was examined by Allen<br />
(1975). In his research conducted in California, using the San Andreas fault system as an<br />
example, he indicated that nearly all large earthquakes with magnitudes greater than 6.0<br />
on the Richter Scale have occurred along existing faults that are associated with active<br />
mountain fronts. Such earthquakes occur at relatively shallow depths (less than 20km)<br />
that are largely associated with subsurface rupture and surface faulting and folding. In<br />
addition, he reported that larger earthquakes have generally occurred on the larger and<br />
longer faults (Allen 1975).<br />
Many studies around the world (Ganas et al. 2001, Tramutoli et al. 2001)<br />
confirmed the strong relationship between active faults and earthquakes and the<br />
usefulness of remote sensing techniques to recognize and analyze that relationship<br />
(Dreger and Kaverina 2000, Karnieli et al. 1996, Sabins 1997, Süzen and Toprak 1998).<br />
Such studies established that tectonism has a geomorphic expression in regions where it<br />
occurs (Gerson et al. 1984).<br />
In Jordan, the primary seismic and tectonic zones are the Dead Sea fault system,<br />
and secondarily the Wadi Araba fault, including the Gulf of Aqaba region (Bender 1974a,<br />
1
Degg 1990, Yücemen 1992). Within the Jordan-Dead Sea Transform (JDT), the majority<br />
of the historical and the 20 th<br />
century instrumental recorded earthquakes, often<br />
accompanied with crustal deformation, are clustered on these two fault systems that are<br />
believed to be associated with active mountain fronts (Abou Karaki 1995, Al-Tarazi<br />
1992, Arieh and Rotstein 1985, Ben-Avraham et al. 2005, Ken-Tor et al. 2001, Klinger et<br />
al. 2000a, 2000b, Olimat 2001) (figure 1.1).<br />
Figure 1.1: Earthquakes in the Jordan-Dead Sea Transform and adjacent areas, 1900-<br />
1980 (Modified from Arieh and Rotstein 1985, figure 3, P. 884).<br />
2
The largest earthquake recorded in the Gulf of Aqaba was on November 22, 1995<br />
and had a moment magnitude of 7.3 and a local magnitude of 6.2 on the Richter Scale<br />
with a depth of 14km and an epicenter off-shore about 60km from the head of the gulf<br />
where the cities of Aqaba and Elat are located (Al-Tarazi 2000, Klinger et al. 1999). This<br />
earthquake was the beginning of a seismic swarm that occurred in the central part of the<br />
Gulf of Aqaba. During this swarm, the Jordan Seismology Observatory (JSO) detected<br />
2,089 earthquakes with magnitudes ranging between 2.0 to 6.2, which strongly affected<br />
the near-shoreline cities (Al-Tarazi 2000).<br />
More recently, on September 9, 2006 at 7:58 am, an earthquake with a local<br />
magnitude of 4.5 on the Richter Scale struck the northern part of the Dead Sea with an<br />
epicenter depth of 7.7km (Zgheylat 2006a). On September 18, 2006 near noon time,<br />
another earthquake with a local magnitude of 4.2 on the Richter scale was detected in the<br />
exact location as the previous quake with an epicenter depth of 7km (Zgheylat 2006b).<br />
Both earthquakes were associated with the natural intersection of the River Jordan and<br />
Al-Zarqa Faults (Zgheylat 2006a, 2006b). Earlier, on January 23, 2005, an earthquake of<br />
local magnitude 3.5 on the Richter Scale occurred in the northern Dead Sea segment, one<br />
of a series of two other quakes with local magnitudes of 2.7 each in the Dead Sea and<br />
Tiberias Lake (also known as the Sea of Galilee or Lake Kinneret). The hypocenters of<br />
the quakes were believed to be a few tens of kilometers below the northern section of the<br />
Dead Sea level (Abu El-Zelouf 2005).<br />
In a similar incident, an earthquake with a magnitude of 4.9 on the Richter Scale<br />
struck Jordan on Wednesday, February 11, 2004. The quake occurred at 11:14am and<br />
lasted for around 20 seconds. The hypocenter was located to the northeast of the Dead<br />
3
Sea with a depth of 20km. The main quake was followed by seven aftershocks with<br />
magnitude of two to three points on the Richter Scale (Husseini 2004). The Jordan<br />
Seismology Observatory in the Dead Sea area detected five seismic events on December<br />
31, 2003 and January 1, 2004. The five earthquakes had maximum magnitudes of 3.8 on<br />
the Richter Scale. Such quakes are considered normal, weak, and occur frequently in this<br />
area. The first quake was recorded at 1:30pm with a magnitude of 3.3 on the Richter<br />
Scale. The strongest quake had a local magnitude of 3.8 while the others recorded 2.5<br />
each, with a depth range of 19 to 8.5 kilometers (Al-Gharaibeh 2004).<br />
Five large earthquakes with a local magnitude of 6.0 or higher are recorded for<br />
the region between the Dead Sea and the Gulf of Aqaba. These include the earthquakes of<br />
A.D. 1068, 1202, 1212, 1293, and 1458 (Ellenblum et al. 1998, Niemi et al. 2001). The<br />
epicenters of the 1068 and 1212 quakes were probably in the southern Araba Valley<br />
(Niemi et al. 2001). Clearly, the occurrence of earthquakes represents a significant<br />
geologic event in the region, with potential significance for the associated human<br />
population.<br />
1.3. Justification of the Study<br />
This study is believed to be the first attempt to apply two geomorphic indices,<br />
namely mountain front sinuosity (S mf ) and valley height to valley floor width ratio (V f ) to<br />
conduct morphometric analysis in the Jordan-Dead Sea Transform zone. Since these<br />
geomorphic indices were first introduced as indicators of seismic activity (Bull and<br />
McFadden 1977), normally all measurements have been collected using topographic and<br />
geologic maps as sources of elevation then manually calculated to determine the indices<br />
values. In this research a new methodology is applied using a digital approach, including<br />
4
satellite imagery, multiple layers of geographic data, and digitized calculations of the two<br />
geomorphic indices of seismic potential to achieve more precise determinations.<br />
Previous studies focused on the Jordan-Dead Sea Transform, including the Dead<br />
Sea and Wadi Araba, employed different analytical techniques and multiple sensors in<br />
their applications, including Landsat TM (Gerson et al. 1984, Malkawi et al. 2000),<br />
Radarsat (Abdelhamid 2001), SPOT imagery and SPOT derived DEM (Klinger et al.<br />
2000a, 2000b), GTOPO30 dataset (Galli and Galadini 2001), digitized topographic maps<br />
(Hall 1997), gravity anomaly maps (Brink et al. 1999), plus paleoseismic analyses<br />
(Marco et al. 2005, Zilberman et al. 2000), GPS geodesy (Wdowinski et al. 2004), and<br />
seismic anisotropy (Rümpker et al. 2003).<br />
This study aims to accomplish the transition from a conventional to digital<br />
morphometric analysis approach in order to determine tectonic activity along the<br />
mountain fronts in the Jordan-Dead Sea Transform Zone (JDTZ) to examine their degree<br />
of activity and add to the repertoire of geomorphic and environmental studies in Jordan.<br />
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)<br />
imagery will be the main source of Digital Elevation Models (DEMs) and an input to<br />
other digital data. Morphometric analysis is being utilized because the results of this<br />
method have proven to be reliable and relatively accurate in the assessment of tectonic<br />
activity of large-scale regional analysis of natural geomorphic forms (Azor et al. 2002,<br />
Silva et al. 2003, Zovoili et al. 2004). In addition, this approach is easy, does not require<br />
expensive equipment, and can be remotely performed without conducting field<br />
measurements.<br />
5
1.4. The Jordan-Dead Sea Transform Zone characteristics<br />
The following section is a brief description of the geomorphology, geology, and<br />
seismicity of the Jordan-Dead Sea Transform zone. Several seismic maps of Jordan and<br />
its vicinity are included to illustrate the relationship between tectonic events and major<br />
faults along the JDTZ, such as earthquakes in Jordan and the surrounding countries,<br />
seismic zones in the area, and the major fault lines located in Jordan.<br />
1.4.1. Geomorphology of the JDTZ<br />
The study area extends from the northern shoreline of the Dead Sea Transform<br />
System, Wadi Araba (Araba or Arava Valley), to the Gulf of Aqaba. The focus is on the<br />
eastern portion of the region that falls only within the Jordanian territories defined by<br />
Jordan’s western borders. Since the study area is part of the Jordan-Dead Sea Rift system<br />
(Dead Sea Transform System, DST) and the Jordan-Wadi Araba Rift including the Gulf<br />
of Aqaba area, it will be referred to as the Jordan-Dead Sea Transform Zone (JDTZ). The<br />
JDTZ extends approximately 245km in length (N-S direction) and about 40km in width<br />
(E-W direction), as illustrated in figure 1.2.<br />
6
Figure 1.2: Jordan-Dead Sea Transform Zone (JDTZ) dimensions; 245km (N-S) and 40<br />
km (E-W).<br />
7
The Jordan-Dead Sea Rift system, that contains the JDTZ, extends over 1,000km,<br />
which is a portion of the original 6,000km East African-North Syrian Fault System that is<br />
also called the East Africa-Asia Rift System (Bender 1974a, 1975, Burdon 1959, Klinger<br />
et al. 2000a) (figure 1.3). The Rift margins show extensive extensional rifts combining<br />
normal faults and flexures. The movement along the Dead Sea Transform began in the<br />
early Miocene during two stages of left-lateral displacement and counterclockwise<br />
rotation of the Arabian plate relative to the African plate (Goudie 2002, Taqieddin et al.<br />
2000), as shown in figure 1.4. This has led to the formation of several pull-apart basins<br />
and push-up swells along the transform. The Dead Sea Basin is the deepest and largest<br />
pull-apart basin along the Jordan-Dead Sea Rift system with active seismicity along the<br />
transform area (Bender 19974b, Niemi et al. 2001, Taqieddin et al. 2000).<br />
Figure 1.3: East African Rift System (Modified from Keller and Pinter 2002, figure 2.17,<br />
p. 69).<br />
8
The Red Sea is essentially a spreading center between the Arabian and Nubian<br />
plates (Garfunkel 1997). Since is it located to the south of the Gulf of Aqaba, the latter is<br />
directly affected by any tectonic activity in the Red Sea. The motion between the Arabian<br />
and Nubian plates is parallel to the total motion of the Red Sea transform (Sultan et al.<br />
1993).<br />
Figure 1.4: Tectonic setting of the Middle East. Arrows show the motion between the<br />
Arabian and African Plates along the Dead Sea Fault (DSF), the North Anatolian Fault<br />
(NAF), and (EAF) East Anatolian Fault (Modified from Goudie 2002, figure 8.1, p. 216).<br />
The breakup of the continuous Afro-Arabian continent during the Cenozoic Era<br />
and the successive drift of Arabia from Africa created a series of rifts reflected by major<br />
morphologic depressions. The Dead Sea rift is mainly a transform boundary, while the<br />
9
Red Sea which is the longest and biggest basin within the Rift system has developed<br />
through a stage of continental extension and is now a spreading boundary (Joffe and<br />
Garfunkel 1987). In fact, most of the spectacular relief and structures in the Middle East<br />
and northeastern Africa are related to the tectonic movements resulting from the opening<br />
of the Red Sea basin (2000km long and 350km wide) that started in the Late Oligocene<br />
about 30Myr (Goudie 2002) (figure 1.5).<br />
Figure 1.5: (A) Wadi Araba Valley location map along the Jordan-Dead Sea Transform<br />
fault system (JDT). (B) Generalized geologic map of Wadi Araba Valley showing<br />
location of selected major active faults and juxtaposition of different bedrock lithologies<br />
across the valley (Modified from Niemi et al. 2001, figure 1, p. 450).<br />
10
Wadi Araba extends about 147km in length (Niemi et al. 2001) and is part of this<br />
depression that is located between the Gulf of Aqaba and the Dead Sea to the northnortheast.<br />
The transform fault strikes N15˚E - N5˚E (Bender 1974b, 1975, 1982). The rift<br />
valley rises gradually from the Gulf to an altitude of about 250m at the watershed of Jebel<br />
er-Risha (75-80km long) and continues about 1,000m from this divide to the southern<br />
shore of the Dead Sea where it decreases to an altitude of 400m-409m below sea level<br />
(Andrews 1996, Bender 1974b, 1975). The width of the valley averages 15km but varies<br />
significantly between 9km at the narrowest part in the south about 16km NNE of Aqaba,<br />
to about 25km in the north at Wadi Feinan (Bender 1974b, 1975, Niemi et al. 2001).<br />
Unconsolidated sediments of Quaternary age and older clastic sediments occupy most of<br />
the Wadi Araba floor (Bender 1974b, 1975, 1982).<br />
The Wadi Araba-Jordan Valley is a transform valley and is distinguished from rift<br />
valleys that are bound by normal faults and escarpments on both sides by having a strikeslip<br />
fault that trends at an angle to the transform valley (Ginat et al. 1998). The highlands<br />
bordering the east side of the Jordan rift valley rise 1,592m in the south at Jebel er-Risha,<br />
about 1,500m above the valley floor, and 1,200m in the north at the east side of the<br />
southern end of the Dead Sea about 1,550m above the level of the Dead Sea (Bender<br />
1974b, 1975). The mountain ridge east of the rift slopes gently eastward in the direction<br />
of the central plateau, while it is very steep on its western side towards the rift where it<br />
reaches 1,734m in height (Bender 1974b, Royal Geographic Center 1992). Many wadis<br />
and perennial streams cut farther eastward into the plateau capturing additional area in<br />
the drainage basins of the rift (Bender 1974b, 1975, 1982).<br />
11
Both the western and eastern sides of the rift valley demonstrate distinct, mostly<br />
triangular-shaped morphological projections and niches of structural origin (Bender<br />
1974b), which could reflect the disharmonic faulting in the Jordan-Wadi Araba graben<br />
(Picard 1952). The eastern scarp of the Dead Sea basin in Jordan is relatively straight and<br />
continuous and is bounded by a single bordering fault (figure 1.6), whereas, the western<br />
side, located in Israel, is more complex with several step faults or fault splinters involved.<br />
Left lateral movement along a curved strike-slip fault is believed to have opened the<br />
Dead Sea pull-apart basin (Bartov and Sagy 2004, Goudie 2002).<br />
Figure 1.6: Block diagram along the central part of the JDTZ illustrating the tectonic<br />
style and the continuous rise of the graben floor (From Kashai and Croker 1987, figure<br />
11, p. 50).<br />
According to Picard (1987), the Aqaba (Elat)-Dead Sea-Jordan subgraben system<br />
(i.e. Jordan-Dead Sea Transform) is divided into four distinct subgrabens namely (1) The<br />
Gulf of Aqaba and South Araba, (2) The North Araba-Dead Sea-South Jordan, (3)<br />
12
Central Jordan Valley and Lake Tiberias, and (4) North Jordan or Hula Valley (figure<br />
1.7). The first two subgrabens are located within the JDTZ, therefore, a brief description<br />
of both geomorphology and geology are included below according to Picard (1987)<br />
interpretations.<br />
Figure 1.7: The Aqaba-Dead Sea-Jordan subgraben system (From Picard 1987, figure 1,<br />
p. 24).<br />
13
1) The Gulf of Aqaba (Elat) graben extends about 180km in length to Tiran, is 15-<br />
25km in width, and is up to 1,850m in depth. It is composed of Precambrian basement<br />
rocks and surrounded by the 2,000m high Sinai and Hedjaz horsts. The Sinai slopes are<br />
cut by Pliocene-Quaternary meridian (N-S) to submeridian (NNE-SSW) normal dip-slip<br />
faults that are sometimes coupled with minor strike-slip faults. Subgraben faults have an<br />
average dip of 70°. The mean width of the graben between the main marginal faults, now<br />
covered by the Red Sea, is 20km (Picard 1987).<br />
2) The North Araba-Dead Sea-South Jordan subgraben is north of the Aqaba-<br />
South Araba subgraben. The former subgraben is distinguished by a 700m altitude<br />
difference from the latter. It stretches roughly 80km in length from the Jebel er-Risha,<br />
watershed that consists of Paleocene-Eocene limestone and marls, down to the Dead Sea<br />
(400 below mean sea level). On the Jordanian (Transjordan) side, a large fault oriented<br />
NNE (20° to 25°) extends from Jebel er-Risha area and is masked by the Araba alluvial<br />
deposits (Picard 1987).<br />
The Jordan-Dead Sea Transform has several structural characteristics which have<br />
been highlighted by several scholars that can be summarized as follow:<br />
1) A major left-lateral offset of about 105-110km has taken place along a belt of<br />
strike-slip faults across the transform (Klinger et al. 2000b, Quennell 1959).<br />
Most of the movement was over by the Quaternary. The offset occurred across<br />
an area several kilometers wide near the Gulf of Aqaba (Picard 1987).<br />
2) Grabens are rhomb-shaped. They appear as depressions in the transform floor<br />
that were produced by strike-slip faults, many of which are en echelon (Picard<br />
1987, Quennell 1959), as shown in figure 1.8.<br />
14
3) Relief of several hundreds to a few thousands meters is present as a result of<br />
normal faulting along the transform margins. As a result, an apparent contrast<br />
between uplifted shoulders and downfaulted stepped blocks exist in a few<br />
locations along the transform margins (Picard 1987) (figure 1.9).<br />
Figure 1.8: A block diagram -not to scale- showing the strike-slip geometry along the<br />
JDTZ representing the en echelon fault system (From Kashai and Croker 1987, figure 15,<br />
p. 57).<br />
15
Figure 1.9: The Seven Pillars of Wisdom of southern Jordan developed on the Cambrian-<br />
Ordovician Sandstones in Wadi Rum located in the Aqaba area (Modified from Goudie<br />
2002, Plate 8.2, p. 227).<br />
1.4.1.1. Rifting Process and Extensional Tectonics<br />
The Jordan-Dead Sea Transform Zone is a rift valley that separates the two<br />
tectonic plates, the Arabian to the east and the African to the west. Rift valleys are<br />
significant landforms associated with continental crust where the lithosphere is<br />
dominated by tensional stress (Summerfield 1997, van der Pluijm and Marshak 1997)<br />
(figure 1.10).<br />
Figure 1.10: The East Africa Rift Valley as an example of the rifting process (From<br />
Keller and Pinter 2002, figure 2.16 (a), p. 68).<br />
16
The structure of rifts include complex normal faults of planar and listric patterns.<br />
The widely accepted and traditional view of the geomorphology of normal faults within a<br />
rift system shows downthrown blocks as grabens bounded by planar normal faults in<br />
which horsts repeat in a symmetric pattern (figure 1.11a). On the other hand, listric faults<br />
produce asymmetric structures with the downthrown block generating a half-graben<br />
structure (figure 1.11b) (Park 1988, Summerfield 1997, van der Pluijm and Marshak<br />
1997).<br />
Figure 1.11: Rift structure (A) symmetric horst and graben structure (B) Asymmetric<br />
listric fault half-graben structure (From Summerfield 1997, figure 4.9, p. 92).<br />
Normal faults in rift systems are generated by tensional tectonic forces due to the<br />
extension of lithosphere (i.e. crustal stretching) at divergent plate boundaries in the<br />
oceanic lithosphere (e.g. Mid-Atlantic Ridge) and in the continental lithosphere (e.g. East<br />
African Great Rift Valley) (Buck 1991, Park 1988, van der Pluijm and Marshak 1997). In<br />
17
most cases, normal faults are composed of parallel arrangements that might be planar or<br />
listric. The movement of a listric normal fault triggers rotation of the hanging wall around<br />
a horizontal axis which forms a rollover anticline. Along listric normal faults, the hanging<br />
wall sloping in the direction of the main fault generates half-graben depressions. This<br />
formation is widely seen in the Basin and Range of the southwestern United States<br />
topography where half-grabens form the basins and the tilted fault block forms the ranges<br />
(figure 1.12a). If normal faults happen in conjugates, planar normal faults will form. In<br />
this case, the block enclosed between them drops down creating a graben, while the<br />
remaining uplifted block to its side will form a horst (figure 1.12b) (Park 1988, van der<br />
Pluijm and Marshak 1997, Wernicke 1981, Wernicke and Burchfiel 1982).<br />
Figure 1.12: Normal fault system (a) Half-graben system (b) Horst and graben system<br />
(From van der Pluijm and Marshak 1997, figure 8.31, p. 173).<br />
The traditional concept of active asymmetric arrangements of horsts and grabens<br />
requires that at some point the displacement of faults will disappear or die out at depth.<br />
The models of asymmetric faulting in rift systems indicate that the listric normal faults<br />
merge at depth with a regionally extensive subhorizontal detachment fault (figure 1.13)<br />
18
(Price 1990, van der Pluijm and Marshak 1997, Wernicke 1981, Wernicke and Burchfiel<br />
1982).<br />
Figure 1.13: (a) Symmetric horst and graben system (b) Half-graben system above the<br />
subhorizontal fault detachment (From van der Pluijm and Marshak 1997, figure 15.5, p.<br />
326).<br />
The JDTZ is distinguished by its large alluvial fans that are normally found in arid<br />
to semiarid regions. Alluvial fans are considered to be an erosional-depositional system<br />
with a surface that has a cone-shape and concave cross-section. They spread out from the<br />
point where the stream leaves the mountain to form cone-shaped bodies. The fan slope is<br />
affected by the stream channel slope, width, and depth that changes discharge patterns<br />
and depositional patterns. All alluvial fans have only one apex (head), which is the<br />
attaching point with the mountain, and end at the toe (Bull 1968, 1977a, Bull and<br />
McFadden 1977, Summerfield 1997). The western side of the JDTZ margins is delimited<br />
by widespread alluvial fan bajadas, as illustrated in figure 1.14. The alluvial fans are<br />
deformed by fault displacement in the JDTZ (Baker 1986b, Rockwell et al. 1984,<br />
Summerfield 1997).<br />
19
Figure 1.14: Alluvial fans (bajadas) at the southern end along the eastern side of Wadi<br />
Araba (Left: Landsat 7 ETM+ 742-composite image; Right: Landsat 7 ETM+ Band-7 of<br />
the JDTZ, 2002).<br />
1.4.2. Structure and Geology of the JDTZ<br />
1.4.2.1. Structure<br />
1.4.2.1.a. Wadi Araba<br />
The Jordan Rift Valley, that includes the Wadi Araba fault, is the single most<br />
important structural feature that extends the whole length of the country and forms<br />
Jordan’s western border (Andrews 1996). The meridional rift valley forms a 200km long<br />
portion of the East African-North Syrian zone of structural weakness. The Wadi Araba<br />
fault system strikes N15°E from the Gulf of Aqaba to the Dead Sea and separates the<br />
Palestine Block in the west from the Transjordan Block in the east. In comparison with<br />
the Palestine block, the Transjordan block is structurally higher, has steeper regional dips<br />
to the north, and drops off more rapidly north of east-west fault zones (Bender 1974b,<br />
1975, 1982). The Wadi Araba fault system illustrates an obvious left lateral strike-slip<br />
fault system with a movement history primarily during mid Miocene and Pliocene-Recent<br />
phases (Andrews 1996, Bender 1975). This strike-slip movement has also led to the<br />
formation of discontinuous and irregular extensional grabens and compressional folds<br />
20
along its length (Andrews 1996). A study conducted by Burdon (1959) suggests that the<br />
tectonism of Jordan was divided into tensional and compressional structures. Several<br />
studies including Burdon’s, have determined five major compressional features in Jordan<br />
(30-80km long) primarily oriented in the NE-SW direction. These are the Wadi El-Yabis,<br />
Wadi Shueib, Biren, Amman-Al-Hallabat, and Al-Shawbak structures that are<br />
constructed of a series of folds and thrust faults (Al-Tarazi 1992). In general, continuous<br />
fault zones exist along both sides of the Jordan-Dead Sea Transform. All major active<br />
fault systems to the east of the rift strike at various angles to the direction of the Jordan-<br />
Dead Sea Transform (Bender 1974b, 1982), forming cliffs and causing occasional<br />
earthquakes in the area and its vicinity (Andrews 1996).<br />
Within the rift valley itself, the major faults are parallel to the direction of the<br />
Jordan-Dead Sea Transform. The network of faults dividing the mountain range east of<br />
the western border faults has the same trend as the border fault system; north, northnorthwest,<br />
northwest, and roughly east-west. The north-trending faults are much longer<br />
than the others. The faults parallel to the direction of Wadi Araba and to a larger scale to<br />
the Jordan-Dead Sea Transform have affected Miocene to Pliocene and Quaternary<br />
sediments within the rift valley. Along the border faults, significant dip-slip movements<br />
have occurred with the down-dropping of the western block often exceeding 500m<br />
(Bender 1974b, 1982).<br />
1.4.2.1.b. The Dead Sea<br />
The Dead Sea, often called the Dead Sea Rift or the Dead Sea Depression (DSD),<br />
is a transform feature between the Red Sea in the south and the collision zone of the<br />
Taurus-Zagros Mountains in the north (Freund 1965). The Dead Sea is about 100km long<br />
21
and 10-15km wide. Its catchment area has the capacity of 40,000km 2 of saline water<br />
(Arkin and Gilat 2000, Garfunkel 1997, Taqieddin et al. 2000). It is a major plate tectonic<br />
feature forming the boundary between the Arabian plate on the east and the African plate<br />
(Sinai subplate) on the west. It is considered a major strike-slip fault that has about<br />
100km of cumulative left-lateral slip. The Dead Sea is the lowest point on Earth (about<br />
400-415m below mean sea level) and it is one of the many basins along the Dead Sea<br />
Transform System that has up to 700m high escarpments. It developed as a wide pullapart<br />
basin containing fluvial and evaporite beds of Miocene to Holocene age about 20-<br />
25Myr to 10kyr (Frumkin 2001, Garfunkel 1997, Klinger et al. 2000a, Quennell 1983,<br />
Taqieddin et al. 2000). The Dead Sea is considered to be a transform depression rather<br />
than a rift because it is bounded by normal faults whose scarps reach 700m and are<br />
accompanied with left lateral strike slip (Zilberman et al. 2000).<br />
The Dead Sea consists of two basins, the northern and southern basins, which are<br />
divided by the Lisan Peninsula. The northern basin, which is larger and deeper, is about<br />
50-60km long and 700-730km below mean sea level. The southern basin is smaller and<br />
shallower, about 30-40km long and 300-350km below sea level, and is almost dry at the<br />
present time (Arkin and Gilat 2000, Garfunkel 1997, Goudie 2002, Taqieddin et al. 2000,<br />
Yechieli et al. 1998) (figure 1.15). The level of the Dead Sea has dropped 20m during the<br />
twentieth century (Arkin and Gilat 2000) with an average annual withdrawal rate of<br />
0.8m/yr (Yechieli et al. 1998). In recent years, the Dead Sea’s southern basin is almost<br />
dry due to mineral harvesting by Potash Companies both in Jordan and Israel. The<br />
northern basin contains saline water with a catchment capacity of about 40,000-<br />
42,000km 2 (Garfunkel 1997, Yechieli et al. 1998).<br />
22
A<br />
B<br />
Figure 1.15: (A) Dead Sea location map showing the two basins (From Arkin 2000,<br />
figure 2, p. 713). (B) Inset map shows the present watershed of the DSD and the general<br />
location of major strike-slip faults along the Dead Sea transform. The DSD is enlarged<br />
showing its flanked escarpment associated with normal faulting along the depression<br />
border (From Frumkin 2001, figure 1, p. 80).<br />
1.4.2.2. Geology<br />
The geology of the Jordan-Dead Sea Transform Zone includes the youngest rocks<br />
(i.e. lake sediments) to be found in Jordan. In general, these rocks were deposited 15000<br />
years ago after extensive lakes diminished during the Late Pleistocene, which occupied<br />
the whole area forming soft siltstones and mudstones. Such rocks have been eroded into a<br />
landscape of gullies and cliffs (Andrews 1996, Ron et al. 2006). Along the fault systems,<br />
younger rocks are down-faulted against older complexes to the east, forming the<br />
23
triangular shaped structural niches, giving the east side of the Jordan-Dead Sea<br />
Transform its distinct structure and morphological characteristics (Bender 1974b, 1982).<br />
The JDTZ, especially Wadi Araba, is occupied entirely by unconsolidated<br />
sediments of Quaternary age and older clastic sediments and limestones. Pre-Cambrian<br />
igneous and metamorphic rocks cover an area of approximately 1,800km 2 in southern<br />
Jordan. These rocks are exposed from the area south of Aqaba for approximately 70km<br />
towards the north along the east side of the Wadi Araba Rift. They are also exposed east<br />
of the Rift and south of the Ras en-Naqab escarpment, dipping east of Wadi Rum<br />
underneath a thick sequence of Paleozoic sandstones (Bender 1974a, 1975, Burdon 1959)<br />
(figure 1.16).<br />
Figure 1.16: Jordan-Dead Sea Fault simplified geological cross-section. (Pε)<br />
Precambrian, (P) Paleozoic, (K) Cretaceous, (E) Eocene, (M) Miocene, and (PL) Pliocene<br />
rocks and sediments (From Ginat et al. 1998, figure 3, p. 154).<br />
The Jordan-Dead Sea Transform Zone basement is mainly divided into the Aqaba<br />
and the Araba complexes separated by a regional unconformity, where the former<br />
complex consists of two units and the latter consists of three units. Figure 1.17 is a<br />
24
simplified geological cross section across the southern section of the Jordan-Dead Sea<br />
Transform near Al-Quwayra town which is located about 35km northeast of Aqaba (Sneh<br />
et al. 1998).<br />
Figure 1.17: A simplified geological cross section across the southern section of the<br />
Jordan-Dead Sea Transform, about 40km northeast of Aqaba (Modified from Sneh et al.<br />
1998).<br />
1.4.2.2.a. The Aqaba Complex<br />
1) Metamorphic Rocks: The metamorphic rocks are found as blocks within the<br />
surrounding Neoproterozoic intrusive rocks. In Wadi Abu Burqa, at Gharandal area, they<br />
were preserved from erosion before deposition of the Cambrian rocks. The metamorphic<br />
rocks are dated as 700-800Myr (Jarrar et al. 1983). This age matches the age obtained for<br />
the metamorphic rocks of the Elat area (Kroner et al. 1990).<br />
2) Igneous Rocks: The igneous rocks consist of highly weathered granites,<br />
granodiorites, and quartz diorite. The plutons of the Aqaba complex have an average age<br />
of 630-580Myr (Ibrahim and McCourt 1995).<br />
1.4.2.2.b. The Araba Complex<br />
1) Sarmuj Conglomerates: The Sarmuj conglomerates occur in very small<br />
outcrops along the lower course of Wadi Abu Burqa, with an exposed thickness of about<br />
40m. They form the base of the Araba complex (Bender 1974a). The unit consists of<br />
25
conglomerates with well rounded clasts of plutonic and metamorphic rocks in a partly<br />
brecciated and arkosic-sandy matrix. The base of the Sarmuj conglomerates is<br />
distinguished by the age of the underlying calc-alkaline granitoids and is dated at 625-<br />
600Myr (Jarrar 1985).<br />
2) Hayyala Volcaniclastic Unit: The volcaniclastic unit is a series of stratified,<br />
steeply east dipping, green weathering tuffs with thin horizons of volcaniclastic<br />
sandstone. They are exposed in the margin of Wadi Araba and overlain with an angular<br />
unconformity by Cambrian sedimentary rocks (Bender 1974a). This unit is believed to be<br />
Late Neoproterozoic in age, dated between 595-550Myr (Ibrahim 1993).<br />
3) Rhyolite Volcanics: The upper part of the rhyolite is highly weathered and cut<br />
by dykes and has intrusive joints that are overlain by Cambrian sandstones. This unit was<br />
first recognized in Wadi Rum and believed to be 550-542Myr in age (McCourt and<br />
Ibrahim 1990).<br />
1.4.2.2.c. The Dead Sea<br />
The Dead Sea floor is covered by Neogene and Quaternary sediments up to<br />
several kilometers thick (Picard 1987). Several studies confirmed that the Dead Sea basin<br />
was found to have 10km of sediments with ages from the Neogene to the present time<br />
(Garfunkel 1997, Niemi 1997). According to Frumkin (2001), the macrostratigraphic<br />
analysis of the sediment that has been recovered from the Cave of the Letters in Israel<br />
(west of the transform) indicates a low deposition of the Dead Sea basin around 10-7Myr<br />
ago.<br />
The early formation of the Dead Sea rift took place at some stage in the<br />
Oligocene. During the Miocene it developed as an elongated sedimentary basin with<br />
26
primarily clastic and some volcanic input from the Oligocene to the Pleistocene, salt<br />
lakes and evaporite deposits were formed, creating the present day Dead Sea. Clastic,<br />
evaporite, alluvial, and lacustrine sediments continued to be deposited throughout the<br />
Pleistocene until today (Arkin and Gilat 2000, Klinger et al. 2000a).<br />
A brief geological description of the rock types and their abundance within the<br />
JDTZ are listed in table 1.1 illustrating the location of the examined mountain fronts and<br />
their proximity to different rock types that consequently will affect the final<br />
morphometric analysis results. Harder rocks (e.g. limestone) are primarily located in the<br />
northern region while mostly softer and weathered rocks (e.g. sandstone), with an<br />
exception to the presence of a small number of fronts along granite mountains, are<br />
present in the southern region, as shown in figure 1.18.<br />
27
Location Rock Type Description<br />
Q 4<br />
Lisan Formation (Jordan Valley) deposited in a lacustrine<br />
environment during the Quaternary that consists of sandstone,<br />
shale, chalk, marl, and conglomerate<br />
βq<br />
Little quantities of olivine basalt, scoria, tuff, and agglomerate<br />
(Quaternary, younger than 1.8Myr)<br />
Dead Sea<br />
Limestone, chalk, chert, marl, and clay (Senonian-Paleocene)<br />
North<br />
Araba<br />
South<br />
Araba<br />
Aqaba<br />
K S<br />
β1<br />
Ja<br />
Q 4<br />
T S<br />
K J<br />
P Mn<br />
Q<br />
P Mn<br />
Q<br />
K K<br />
P Mn<br />
G C<br />
Magmatic intrusions of alkali basalt (Jurassic-Lower Cretaceous:<br />
few scattered quantities within the Lisan Formation)<br />
Limestone, dolomite, and sandstone (Upper Zarqa Group, Jurassic)<br />
Lisan Formation (Jordan Valley) deposited in a lacustrine<br />
environment during the Quaternary that consists of sandstone,<br />
shale, chalk, marl, and conglomerate<br />
Limestone, clay, marl, gypsum, and conglomerate (Late Eocene-<br />
Pliocene)<br />
Limestone, dolomite, and marl (Late Cretaceous: Cenomanian-<br />
Turonian)<br />
Sandstone (little quantity) mainly with existence of clay and<br />
dolomite (Cambrian-Turonian)<br />
Undifferentiated Alluvium (Quaternary), most abundant bedrock<br />
Sandstone mainly with existence of clay and dolomite (Cambrian-<br />
Turonian)<br />
Undifferentiated Alluvium (Quaternary), most abundant bedrock<br />
Sandstone: massive and brownish weathered sandstone (Lower<br />
Cretaceous)<br />
Sandstone mainly with existence of clay and dolomite (Cambrian-<br />
Turonian)<br />
Granite: gray granite and alkali granite (Precambrian)<br />
Table 1.1: Concise description of the mountain fronts rock types within the JDTZ<br />
(Modified from Bartov 1990 and Bender 1974b).<br />
28
Figure 1.18: Rock types and the locations of all mountain fronts in the JDTZ study area.<br />
29
1.4.3. Seismicity of the JDTZ<br />
1.4.3.1. Regional tectonics of Jordan and its vicinity<br />
The Levant is a unique region in terms of documenting historical earthquakes that<br />
covers the time span of four millennia. This documentation is in a variety of forms that<br />
includes biblical, Roman ecclesiastical, and Islamic and Arabic historical chronicles.<br />
During the last 4,000 years, several destructive earthquakes occurred over large areas of<br />
the Middle East region that caused loss of life and property (Abou Karaki 1995, Al-<br />
Tarazi 1992, Degg 1990). A thorough analysis of the earthquakes that affected Northwest<br />
Arabia (modern Jordan, Palestine, and Israel) from the 2 nd to the mid-8 th century A.D.<br />
was conducted by Russell (1985) from historical records and archaeological evidence<br />
collected in these countries. Destructive earthquakes occurred during the late Roman,<br />
Byzantine, and Early Islamic periods in Northwest Arabia, and were generated as a result<br />
of the existence of border faults and other structural elements along the rift valley that are<br />
capable of producing seismic activity (Russell 1985).<br />
The tectonism of Jordan is directly related to the regional tectonism in the Middle<br />
East and the Eastern Mediterranean region, which is mainly controlled by the Jordan-<br />
Dead Sea Transform fault system (Al-Tarazi 1992). Much of Jordan is subject to a<br />
momentous seismic threat that has been reported in contemporary geological and<br />
seismological investigations and also mentioned throughout ancient documents. During<br />
the past 80 years, seismic activity in Jordan has been relatively low; however, the whole<br />
region has been affected by earthquakes for thousands of years. An excellent example is<br />
the 1927 earthquake with a local magnitude of 6.25 on the Richter scale, which was<br />
devastating in several locations (Arieh et al. 1982, Avni et al. 2002, Ben-Menahem 1991,<br />
30
Marco et al. 1996, Niemi and Ben-Avraham 1994, Vered and Striem 1977). The main<br />
concern is that the major Jordanian cities and highly populated regions such as Amman,<br />
Irbid, Salt, Aqaba, Jarash, Al-Karak, Al-Mafraq, Al-Tafila, Ghour es-Safi, and Petra are<br />
located in earthquake-prone areas within proximity of active fault systems that branch off<br />
the JDT such as Carmel, Al-Karak, Al-Fiaha, Wadi El-Sirhan, Zarqa Main, and Swaqa<br />
faults (Abou Karaki 1995, Klinger et al. 2000b, Olimat 2001, Quennell 1958, Yücemen<br />
1992). Obviously, the most populated areas within this region are vulnerable to strong<br />
earthquakes, generating a real threat to the safety of population, infrastructure, social<br />
integrity, and economics of Jordan and its surrounding countries (Olimat 2001).<br />
The strongest earthquake activity zone in terms of magnitude and frequency is the<br />
Jordan-Dead Sea Transform fault system, which is considered an active tectonic feature<br />
based on the region’s seismicity (Yücemen 1992). The seismicity of Jordan-Dead Sea<br />
Transform system is considered to be low to moderate; nevertheless, several destructive<br />
earthquakes have occurred in the past that destroyed most of the urban areas in Jordan<br />
and the surrounding countries such as those in A.D. 362, 748, 1033, 1034, 1070, 1182,<br />
1201, 1759, 1837, 1927, 1956, 1995 (Al-Tarazi 1992, Olimat 2001).<br />
The primary seismic and tectonic threat in Jordan is derived from the Dead Sea<br />
fault system, and secondarily the Wadi Araba fault (Bender 1974a, Yücemen 1992).<br />
Paleoseismic analysis of the Azaz fault segment of the Dead Sea Rift indicates that this<br />
region was subjected to irregular periods of strong seismicity and quiescence during the<br />
latest Pleistocene and the Holocene. At least two large earthquakes occurred in the Early<br />
Holocene, each one resulting in a 1-1.5m high fault scarp (Zilberman et al. 2000). In a<br />
recent study, paleoseismic analysis of the Bet-Zayda Valley in the delta of the Jordan<br />
31
River at the north shore of the Sea of Galilee along the Dead Sea Transform exposed<br />
several stream and surface offsets as a result of the earthquakes that occurred in the area.<br />
The three-dimensional excavations of buried stream channels at Bet-Zayda demonstrate<br />
primarily strike-slip displacement at a minimum rate of 3mm/yr during the Late Holocene<br />
(Marco et al. 2005).<br />
The displacement along the Jordan-Dead Sea Transform was measured from the<br />
displacement of several alluvial fans within the transform. For example, the study of the<br />
Dahal area along Wadi Dahal fault revealed an offset of the largest alluvial fan (i.e. Dahal<br />
fan). The average slip rate of the Dead Sea fault is 4±2mm/yr, corresponding to about<br />
500m of offset since the last interglacial period, consistent with the relative motion<br />
between Arabia and Africa and regional kinematics measured by other techniques<br />
(Klinger et al. 2000a) such as the GPS data north of the Dead Sea (Pe’eri et al. 1998) and<br />
in northern Arabia (Reilinger et al. 1997, Pe’eri et al. 1998), the satellite laser ranging<br />
(SLR) measurements in Israel (Smith et al. 1994), and the data from the offset Plio-<br />
Pleistocene alluvial terraces analysis in the Wadi Araba (Ginat et al. 1998).<br />
In a similar study, Niemi et al. (2001) measured cumulative displacement of 22-<br />
54m from stream channels and alluvial fan surfaces across the Wadi Araba fault using<br />
detailed geologic and topographic mapping. The northern Wadi Araba fault maintained a<br />
relatively constant slip rate in the past 15kyr. The average slip rate of 4.7±1.3mm/yr was<br />
measured from offset fault-scarp alluvial fans. The cumulative displacement as a result of<br />
the last M W 7 earthquake was 3m. Using an average slip rate of 4.7±1.3mm/yr together<br />
with a 3m slip-per-event suggests a maximum earthquake recurrence interval for M L 7<br />
events of Wadi Araba fault of 500-885 years (Niemi et al. 2001). The total displacement<br />
32
along the Jordan-Dead Sea Transform (JDT) caused by left-lateral strike-slip is 107km.<br />
The left-lateral displacement along the JDT occurred in two steps: (1) 62km offset by<br />
Early Miocene (about 18Myr), and (2) 45km offset since the Late Miocene or Pleistocene<br />
to the present time (Niemi et al. 2001). The rotation rate of the Arabian plate was found<br />
to be 0.396˚Myr -1 around a pole at 31.10˚N, 26.70˚E relative to Africa (Klinger et al.<br />
2000a, Quennell 1983).<br />
Regional seismicity studies in Wadi Araba and the Dead Sea fault systems reveal<br />
much information regarding their activity and contribution to historical earthquakes in<br />
Jordan, Palestine and Israel. In an attempt to shed view on the anatomy of the regional<br />
plate boundary, a new gravity anomaly map of Wadi Araba and the southern half of the<br />
Dead Sea transform was produced by Brink et al. (1999) as shown in figure 1.19. The<br />
map highlights a string of numerous subsurface basins of various length, size, and depth<br />
along the plate boundary and relatively short (25 to 55km) and discontinuous fault<br />
segments that occupy the whole transform. Such structure suggests a dynamically<br />
changing plate boundary with time with continuous small changes in relative plate<br />
motion (Brink et al. 1999).<br />
1.4.3.2. Seismotectonic maps of Jordan<br />
The earthquake events that occurred in Jordan and the surrounding countries<br />
between 19A.D. and the end of the year 2005 indicate a significant concentration along<br />
the Jordan-Dead Sea Transform Zone. However, the collected seismic events show a<br />
lower concentration in the eastern part of the Mediterranean Sea when compared to the<br />
earthquake distribution of the major tectonic features in Jordan-Dead Sea Transform area.<br />
According to Al-Tarazi (1992) and based on several earlier studies conducted by Abou-<br />
33
Karaki (1987), Arieh (1991), Ben-Menahem (1979, 1981), Ben-Menahem et al. (1982),<br />
El-Isa and Al-Shanti (1989), and Poirier and Taher (1980), thirteen seismic zones were<br />
identified in Jordan and the surrounding countries of the Middle East. Below is a brief<br />
description of the seismic zones as shown in the seismotectonic map of Jordan and its<br />
vicinity (figure 1.20A) (Al-Tarazi 1992):<br />
Figure 1.19: Bouguer gravity anomaly map of Dead Sea transform, Jordan and Israel,<br />
corrected with density of 2670 kg/m 3 . Contour interval is 3 mGal. Terrain correction was<br />
calculated from digital terrain model (DTM) with 25m grid using inhouse code.<br />
Background: Shaded relief topography from DTM. Top inset is simplified plate geometry<br />
and location of maps. Bottom inset is a regional Bouguer gravity map of Israel and<br />
Jordan (From Brink et al. 1999, figure 1).<br />
34
1. Dead Sea-Jordan River fault (zones 1 and 2): It extends about 200km from 30.90º<br />
to 32.93ºN at a longitude of 35.50ºE that stretches from the Dead Sea along<br />
Jordan River and ends at Tiberias Lake in the north. This fault is characterized by<br />
high seismic activity. Many historical earthquakes occurred along its length. Also,<br />
earthquake epicenters occur along several active faults that branch from the main<br />
fault (figure 1.21).<br />
2. Wadi Araba fault (zone 3): It extends about 174km from the Dead Sea to the Gulf<br />
of Aqaba. The historic earthquake activity along this fault indicates that this fault<br />
is seismically less active than the Jordan-Dead Sea fault.<br />
A<br />
B<br />
Figure 1.20: (A) the thirteen seismic zones and (B) major faults within seismic zones in<br />
Jordan and its vicinity (From Al-Tarazi 1992, map 2.13, p. 49 and map 2.17, p. 53,<br />
respectively).<br />
35
3. The faults of the northern zone (zone 4): The northern zone extends from 30.93º<br />
to 35.00ºN and includes the Ed-Damur, Yammouneh, and Rachaya faults. The<br />
historic earthquakes show that this zone used to be more seismically active than<br />
the Jordan-Dead Sea fault but became less active with time.<br />
4. The faults of the northern Red Sea and the Gulf of Aqaba (zones 5, 6, and 7): The<br />
Red Sea Fault system includes both the faults of the Gulf of Aqaba and the Suez<br />
Gulf that are characterized by seismic swarm activity. However, the seismicity of<br />
the Gulf of Aqaba and the Red Sea zone is lower than of the Jordan-Dead Sea<br />
fault as indicated from the recorded earthquakes.<br />
5. The Wadi El-Sirhan Basalt Area (zone 8): This zone is located to the east of the<br />
Jordan-Dead Sea Transform. It is completely covered by basaltic material and<br />
characterized by slight seismicity.<br />
6. The Wadi Farah-, Carmel-, and Al-Galiel-zones (zones 9, 10, and 11): These three<br />
faults are considered secondary faults that are located to the west of the Jordan-<br />
Dead Sea Transform. The Wadi Farah fault seems to be active compared to the<br />
Carmel and Al-Galiel faults that are less seismically active. Most of the seismic<br />
activity in these faults occurs in swarms that never produced a historic devastating<br />
earthquake. However outlining them is essential as they are situated in a very<br />
densely populated area.<br />
7. The South-East Mediterranean zone (zone 12): This seismic zone was delineated<br />
based on the instrumental earthquake data recorded from this area. The seismic<br />
activity in this zone seems to be low and shallow in comparison to the Jordan-<br />
Dead Sea Transform zones.<br />
36
8. The Cyprus zone (zone 13): It covers the major earthquakes in and around Cyprus<br />
Island. The historical earthquakes recorded in this zone indicate that the Cyprus<br />
fault is active.<br />
The lines in figure 1.20B represent the major faults in the region. According to the<br />
seismotectonic maps of Jordan, the earthquake epicenters are well located along faults<br />
number 1, 2, 5, 8, 9, 10 and 11, while there is random distribution of the earthquakes<br />
epicenters in the proximity of the remaining faults (3, 4, 6, 7, and 12) (Al-Tarazi 1992).<br />
Figure (1.21): The Dead Sea fault and the adjacent branching faults, 1900-1980<br />
(Modified from Brew 2001, figure 4.9, e).<br />
1.4.3.3. Seismic maps of the JDTZ<br />
The Jordan Seismological Observatory began operation to collect and document<br />
seismic data in September 1983. The earthquakes were recorded in digital mode and<br />
processed at the Natural Resources Authority in Amman. All seismic data include the<br />
origin times, magnitude, epicenters in geographic locations (degrees and minutes), and<br />
37
focal depths (hypocenters) in kilometers (JSO 2005). After more than twenty years<br />
(1983-2005) of continuous operation of the seismic network in the region, more than<br />
10,000 earthquakes were recorded in Jordan, mostly distributed along the Jordan-Dead<br />
Sea Transform Zone where most of the mapped active fault zones in the region are<br />
(Olimat 2001) (figure 1.201). An earthquake catalog of the Middle East countries was<br />
compiled from seismic events between 1900 and 1983. This catalog was used to create a<br />
seismic map of the Middle East including the Arab countries located in northern Africa<br />
(Riad and Meyers 1985, Riad et al. 1985). Figure 1.22 is a modified map from Riad and<br />
Meyers (1985) that shows the seismic events in Jordan and surrounding countries during<br />
that period of time.<br />
Figure 1.22: Seismic map of the Middle East 1900 – 1983 (Modified from Riad and<br />
Meyers 1985).<br />
38
A new computerized regional tectonic map of Jordan and the neighboring<br />
countries was produced, which shows the main regional structures in Jordan and the<br />
surrounding area. The purpose of this map is to illustrate the seismic networks that exist<br />
in Jordan and surrounding countries and to show the relationship between earthquakes<br />
and active faults in the JDTZ. The maps shown in figure 1.20 were georeferenced in<br />
ArcGIS. The active fault lines and seismic zones were then digitized to create layers for<br />
more accurate manipulation that could be presented on a seismic map (figure 1.23). In<br />
addition, using the provided earthquake data, two maps were generated of Jordan and the<br />
surrounding countries that show the distribution of earthquake epicenters and their local<br />
Richter magnitudes.<br />
All earthquakes were recorded in local magnitude (M L ) scale which is basically<br />
the Richter magnitude scale that quantifies the amount of seismic energy released by an<br />
earthquake (Richter 1935). Earthquakes of local magnitude of four and greater (M L ≥ 4)<br />
only were mapped. These types of events are noticeable and could cause shaking of<br />
indoor items, rattling noises, and some damage, but no major destruction (Richter 1935).<br />
The major earthquakes maps are presented to illustrate the magnitudes of the seismic<br />
events over time based on the method of collecting the data (figures 1.24 and 1.25) where<br />
all seismic events are represented using circle proportional symbols (Dent 1999).<br />
Historical earthquake data as well as data from 19A.D. to August 1983 were<br />
compiled from multiple published references that studied and recorded the seismicity of<br />
the Middle East including Jordan. The magnitudes of these seismic events were translated<br />
from the Mercalli Intensity Scale, which is based on the observed historic structural<br />
destruction, to the approximate Richter Scale magnitudes (JSO, Personal<br />
39
communication). Some of the previous earthquake catalogues and sources are:<br />
Ambraseys (1978), Amiran (1951, 1952), Ben-Menahem (1991), Gutenberg and Richter<br />
(1956), Karnik (1969), Poirier and Taher (1980), Riad and Meyers (1985), the Bulletin of<br />
the International Seismological Centre (ISC), the Bulletin of Preliminary Determination<br />
of Epicenters (PDE), and the National Earthquake Information Service (NEIS) Bulletin<br />
provided by United States Geological Survey (USGS).<br />
Earthquake data from September 1983 to 2005 were mostly recorded by the<br />
Jordan Seismological Observatory (JSO) stationed at the Natural Resources Authority<br />
(NRA) in Amman, Jordan. Data were delivered in a simple text format (*.txt) with<br />
information such as date of activity (day, month, year), time of occurrence, latitude, and<br />
longitude of earthquake events and their local magnitudes and depth in kilometers (JSO,<br />
Personal communication).<br />
In addition, contemporary earthquakes events of the Middle East region, in Jordan<br />
in particular can be obtained from Jordan Seismological Observatory (JSO), the United<br />
States Geological Survey (USGS), the British Geological Survey (BGS), Israel<br />
Geological Survey (IGS), the Helwan Observatory, Cairo, Egypt (Degg 1990), and the<br />
Institute of Petroleum Research and Geophysics (IPRG) bulletin in Holon (Al-Tarazi<br />
1992).<br />
40
Figure 1.23: Seismic zones and active faults of Jordan and surrounding countries.<br />
41
1.4.3.4. Jordan/JDTZ earthquakes data<br />
Earthquake data presented in the seismic maps of Jordan and within the JDTZ are<br />
as accurate as their source material. Earthquake data included in the tectonic maps covers<br />
Jordan and its vicinity that lie between longitude 32.00°-39.00° east and latitude 27.00°-<br />
35.50° north (all coordinates are in decimal degrees). Magnitude measures the strength of<br />
an earthquake as recorded by a seismometer (Richter 1935). In order to keep all map<br />
earthquake data consistent, local magnitude (M L ) values were used due to their<br />
availability in all seismic data sets. The local magnitudes (M L ) are given for every<br />
recorded seismic event, while intensity values, if available, are in modified Mercalli<br />
intensity scale. The accuracy in the focal depth is proportional to the date and size (i.e.<br />
magnitude) of the recorded earthquakes. In case no determination is possible, depths were<br />
recorded as 0km. The accuracy of the epicentral location is classified according to the<br />
date as follows:<br />
1) 1A.D.-1899: For this period, which includes the historical earthquakes, the<br />
accuracy is expected to range between 50 and 150km.<br />
2) 1900-1980: ±10 km for events lying in between longitude 35.00°-36.00°E and<br />
29.50°-33.00°N, (longitude 53°03’60”E and latitude 29°53’30”N), while for the other<br />
events ±15-25 km.<br />
3) 1981-2005: ±5 km for events between longitude 35.00°-36.00°E and 29.50°-<br />
33.00°N, (longitude 53°03’60”E and latitude 29°53’30”N), while for the other events<br />
±10-15 km.<br />
All earthquake raw data were converted from their formats into Microsoft Office<br />
Excel format (*.xls). Redundant and missing values were eliminated. After that, data<br />
42
were converted into database (dBase IV) format (*.dbf) to be readable by the Geographic<br />
Information System software (i.e. ArcGIS). The earthquake data were imported into<br />
ArcGIS using “Add XY Data” under the “Tools” function where the X axes were<br />
assigned the longitude values and the Y axes assigned the latitude values. Finally,<br />
shapefiles were created for each set of the seismic data (data were assigned the same<br />
coordinate system as the geographic layers of the study area) and recorded on the seismic<br />
maps of Jordan.<br />
All seismic data are projected to the European Datum of 1950 Zone 36 North, the<br />
mean datum for Jordan and Israel, as shown in figures 1.24 and 1.25. All vector data are<br />
projected to the World Geodetic System (WGS) of 1984 ellipsoid and datum, Zone 36<br />
North, under the Universal Transverse Mercator (UTM) coordinate system.<br />
43
Figure 1.24: Major earthquake events on Jordan, 19 A.D. – August 1983.<br />
44
Figure 1.25: Major earthquake events on Jordan, September 1983 – 2005.<br />
45
2. Chapter Two: Literature Review<br />
2.1. Introduction<br />
2.1.1. Morphometric analysis in geomorphology<br />
Mountain fronts, valleys, and alluvial fans are surface features that construct the<br />
arid to semiarid landscape and exist at large or small scales. To understand the way<br />
landforms evolve, it is essential to study the underlying geology. In general, landform<br />
development implies deep structures of the earth; therefore there is always a strong<br />
relationship between landscape and the geologic environment (Keller and Pinter 2002). In<br />
recent years, the advancements in computer technologies and digital data<br />
acquisition/processing has led to the improvement of the knowledge of geomorphic<br />
processes and the development of the use of predictive models and quantitative<br />
measurements to analyze, monitor, and understand landform changes (Summerfield 1997,<br />
Wood 1996). This advancement has allowed geographers, geologists, and<br />
geomorphologists to explore human/land interaction utilizing modeling and systems<br />
analysis in their geomorphological studies that relied on sophisticated hardware and<br />
software tools (Baker 1986a).<br />
The study of the nature of landforms, landscapes, and surface processes including<br />
their description, classification, origin, development, and history highlighting the<br />
physical, biological, and chemical aspects is known as geomorphology, which may have<br />
either a qualitative or quantitative representation (Baker 1986a, Easterbrook 1999, Keller<br />
and Pinter 2002, Morisawa 1985). According to Morisawa (1985), quantitative<br />
geomorphology represents a new subfield of geomorphology that is defined as “the<br />
application of mathematics and statistical techniques to the study of landforms, their<br />
46
description and the processes by which they are created and changed”. Hence, the<br />
quantitative measurement and analysis of landforms and topography are the fundamental<br />
factors of morphometry (Hayden 1986, Keller and Pinter 2002) or geomorphometry<br />
(Summerfield 1997) that summarize numerical definitions of the Earth’s surface shape in<br />
correlation with landscape processes. Morphometric analyses in tectonic geomorphology<br />
studies basically refer to the measurement on topographic maps (recently DEMs) of<br />
quantitative parameters (Wells et al. 1988).<br />
Geomorphology is a significant tool in tectonic studies when using the<br />
geomorphic record. Such record includes several landforms and the Quaternary deposits<br />
that capture immense amount of information from the last few thousands and extend to<br />
about two million years (Keller and Pinter 2002). Tectonic geomorphology focuses on<br />
the contrast between topography and geomorphic features generated by tectonic<br />
processes and the erosion factors caused by surface processes that tend to wear them<br />
down. Defining the relationship between theses processes and interpreting the resulting<br />
landscape features is the main focus of tectonic geomorphology (Baker 1986a, Bull 1984,<br />
Burbank and Anderson 2001).<br />
Major progress in the field of tectonic geomorphology has been made during the<br />
last three decades, primarily due to the increased potential of evaluating the time factor in<br />
landscape development (Bull 1984). Therefore, through the use of computerized models<br />
of landform change, it is possible to determine the magnitude and frequency of<br />
displacements along faults and allocating classes of relative tectonic activity (Baker<br />
1986a). Consequently, tectonic geomorphology might be defined into two categories: (1)<br />
the study of landforms formed by tectonic processes; focusing on the shapes and origins<br />
47
of landforms as a result of tectonic activities, or (2) the application of geomorphic<br />
principles to explain tectonic problems; analyzing landforms to evaluate the history,<br />
magnitude, and rate of tectonic processes (Keller and Pinter 2002). The current research<br />
mainly deals with the second definition of tectonic geomorphology that involves using<br />
geomorphological indices to analyze existing landforms, namely mountain fronts and<br />
their associated valleys, in an effort to determine their tectonic activity classes.<br />
2.1.2. Remote sensing and GIS uses in geomorphology<br />
Earth-observing satellites, airborne sensor systems and aerial and space<br />
photography have nearly complete coverage of the Earth’s surface that provides images<br />
of different formats and various scales. This permits not only interpretation of landscape<br />
evolution, but rather offers the opportunity to integrate observation of a variety of<br />
processes over a large region. Geomorphic analysis from space has the advantage of<br />
allowing the use of quantitative methods for both data gathering and information<br />
extraction. Thus, satellite images are becoming useful and necessary in geomorphology,<br />
especially in obtaining quantitative measurements and performing geomorphic analyses<br />
(Hayden et al. 1986, Ulrich et al. 2003).<br />
Geographic Information Systems (GIS) have enhanced the applicability of<br />
geologic mapping when integrated with data obtained by remote sensing using a wide<br />
range of formats and scales. In addition, advancement in image analysis provides<br />
geologists opportunity to enhance, manipulate, and combine digital remotely-sensed data<br />
with several types of geographic information that in turn increases the amount of<br />
extracted information related to topographic and geologic features (Horsby and Harris<br />
48
1992). Satellite imagery permits research at different scales, which is valuable in the<br />
investigation of lineaments and faults (Arlegui and Soriano 1998).<br />
Digital enhancement of satellite images yields much information about image<br />
features. GIS techniques enable the integration and analysis of multi spatial and nonspatial<br />
data that have the same georeferencing scheme. Therefore, the integration of GIS<br />
and remotely sensed data could be more informative and results would be more<br />
applicable to image interpretation (Ehler 1992, Horsby and Harris 1992, Saraf and<br />
Choudhury 1998). Within the context of GIS, surface geomorphology is most commonly<br />
represented in Digital Elevation Models (DEMs) especially when quantitative<br />
measurement using geomorphometry is necessary. DEMs are generally defined as a<br />
regular two dimensional array of heights sampled above some datum that describes a<br />
surface (Wood 1996).<br />
On remotely sensed images, faults and edge segments (i.e. lineaments) are<br />
generally formed by an assortment of landscape elements that represent rock features on<br />
the land surface. Virtually all lineaments are discontinuous but due to the narrowly<br />
spaced edge and line segments, the human eye tends to merge them together to make<br />
them look continuous (Moore and Waltz 1983). Analyzing faults using remote sensing<br />
data is essential to fields such as tectonics, engineering geology, and geomorphology<br />
especially as they relate to tectonic analysis and earthquake hazards<br />
assessment/mitigation (Süzen and Toprak 1998).<br />
Tectonism in general has a geomorphic expression in the region where it occurs<br />
and its adjacent areas (Gerson et al. 1984). Any subsurface features such as faults,<br />
fracture zones, geological contacts, and numerous bedrock discontinuities have a<br />
49
significant surface expressions that can be detected by extensive analysis of digital<br />
satellite images and photographs that show linear or curvilinear topographic depression<br />
(Hardcastle 1995).<br />
The geomorphology of mountain fronts reveals much information regarding the<br />
tectonic activity occurring along them as well as their past history. Typically, earthquakes<br />
are concentrated on detached mountain fronts (Keller and Pinter 2002). In addition,<br />
alluvial fans are conical landforms characteristic of arid to semiarid regions and are<br />
associated with mountain fronts. They also commonly reveal insights into recent tectonic<br />
activity (Bull 1968, 1977a, Bull and McFadden 1977). Sediments eroded from the<br />
mountain are trapped at the mountain front to shape an endpoint of an erosionaldepositional<br />
system that forms a fan-shaped body. The connecting link between the<br />
depositional and erosional system is the stream. Many features contribute to the<br />
morphology of an alluvial fan, including the size of the drainage basin supplying<br />
sediments to the fan, source area geology, source area relief, vegetation, climate, and<br />
tectonic activity (Bull 1968, 1977a, Bull and McFadden 1977, Keller and Pinter 2002).<br />
2.2. Morphometric analysis approach<br />
Calculation of geomorphologic indices has been applied at different places around<br />
the world. However, there have been no serious attempts to employ this technique in a<br />
digital format rather than applying the broadly used conventional methods of William B.<br />
Bull (Bull 1968, 1977a). While this method of landform analysis has proven to be very<br />
valuable in tectonic investigations, no studies have been found that were carried out in<br />
the Middle East to examine its usefulness using either conventional or digital methods.<br />
50
The study of landforms and deposits developed or modified by tectonic processes<br />
can provide relevant information about the activity of the related tectonic structure. The<br />
geomorphic analysis of mountain fronts, related drainage network, and alluvial fan<br />
systems, provides valuable insights about the recorded tectonic history of any given<br />
region. Therefore, such studies at a regional scale have been frequently undertaken using<br />
morphometric analysis to calculate tectonic geomorphic indices. The most common<br />
indices are mountain front sinuosity (S mf ) and valley floor width to height ratio (V f ) that<br />
when combined together allow individual mountain fronts to be assigned to different<br />
tectonic activity classes (Bull 1968, 1977a, 1978, Bull and McFadden 1977, Silva et al.<br />
2003).<br />
In this approach, the measurements are normally calculated manually from<br />
topographic maps and/or aerial photographs. The elevation measurements for the valley<br />
height are obtained by using topographic maps. In general, these measurements are<br />
compared to measurements obtained in the field to determine their accuracy and<br />
consistency (Bull 1968, 1977a, 1978, Bull and McFadden 1977).<br />
2.3. Geomorphic indices of active tectonics<br />
Geomorphic indices were developed to acquire tectonic information about active<br />
tectonics in areas experiencing rapid deformation and to quantify the description of<br />
landscape (Bull 1977b, Bull and McFadden 1977, Keller and Pinter 2002, Zovoili et al.<br />
2004). In tectonic studies, geomorphic indices are valuable because the needed data can<br />
be easily attained from topographic maps and aerial photographs, plus they can be<br />
employed for evaluation of large areas. The results of the indices of an area might be<br />
51
combined together, or along with other information such as uplift rates to construct its<br />
tectonic activity classes (Bull 1977b, Keller and Pinter 2002).<br />
Below is a brief description of the most common geomorphic indices used in<br />
active tectonic studies. The description includes the index definition/explanation,<br />
mathematical formula, and tectonic geomorphological application.<br />
2.3.1. The Hypsometric Curve and Hypsometric Integral (H i )<br />
The hypsometric curve portrays the distribution of elevation across an area of<br />
land. One advantage of the hypsometric curve is that drainage basins of different sizes<br />
can be compared with each other as a function of elevation and area based on total<br />
elevation and total area plotted under the curve. This makes the hypsometric curve totally<br />
independent of differences in basin size and relief. Thus, the hypsometric curve scale<br />
could range from a single drainage to continents and even to the entire globe (Keller and<br />
Pinter 2002, Strahler 1952).<br />
The hypsometric curve is generated by plotting the relative drainage basin height<br />
(h/H) that is known as the total basin height ratio against the relative drainage basin area<br />
(a/A) which is the total basin area ratio (Keller and Pinter 2002, Strahler 1952). The<br />
maximum height (H) equals the maximum elevation minus the minimum elevation and<br />
represents the relief within the basin. The areas in between each pair of adjoining contour<br />
lines symbolize the total surface area of the basin (A). The area (a) is the surface area<br />
within the basin above a certain line of elevation (h). The relative area (a/A) value<br />
measures between 1.0 at the lowest point in the basin where relative height (h/H) equals<br />
zero, and zero at the highest point in the basin where relative height (h/H) equals 1.0<br />
(Keller and Pinter 2002, Mayer 1990, Strahler 1952), as illustrated in figure 2.1.<br />
52
Determining the hypsometric integral (H i ) is the simplest way to characterize the<br />
shape of the hypsometric curve for a given drainage basin. It is simply defined as the area<br />
under the hypsometric curve and calculated as follow:<br />
H =<br />
i<br />
mean elevation - minimum elevation<br />
maximum elevation - minimum elevation<br />
Calculating the hypsometric integral (H i ) is achieve by deriving the maximum and<br />
minimum elevation directly from a topographic map. The mean elevation is calculated by<br />
obtaining the mean of at least 50 elevation values in the basin using point sampling on a<br />
grid (Keller and Pinter 2002, Pike and Wilson 1971). It can also be evaluated directly<br />
from the digital elevation model (DEM) of the basin (Keller and Pinter 2002, Luo 2002,<br />
Luo and Howard 2005, Pike and Wilson 1971). The hypsometric integral and its<br />
relationship to the degree of dissection allows it to be used as an indicator of a<br />
landscape’s stage in the cycle of erosion. The theoretical evolution of the stage of a<br />
landscape is: (1) youthful stage, characterized by deep incision and rugged relief, (2)<br />
mature stage, where various geomorphic processes operate in near equilibrium, and (3)<br />
old stage, distinguished by a landscape near base level with very subdued relief. High<br />
hypsometric integral values indicate that most of the topography is high relative to the<br />
mean representing a youthful topography stage. Intermediate to low hypsometric integral<br />
values represent more evenly dissected drainage basins, indicating a mature stage of<br />
development (Keller and Pinter 2002, Mayer 1990, Strahler 1952).<br />
53
Figure 2.1: Hypsometric curve derivation from drainage basin (From Keller and Pinter<br />
2002, figure 4.1, p. 122).<br />
2.3.2. Drainage Basin Asymmetry (AF)<br />
Active tectonic deformation has its effect on the development of adjacent<br />
drainage basins. Such stream networks have distinctive patterns and geometries that can<br />
be described both qualitatively and quantitatively (Hare and Gardner 1985, Keller and<br />
Pinter 2002). Studying drainage systems provides information on the long-term evolution<br />
of the landscape (Burbank and Anderson 2001).<br />
The asymmetry factor (AF) was developed to detect tectonic tilting transverse to<br />
flow at drainage-basin or larger scales (Hare and Gardner 1985, Keller and Pinter 2002).<br />
The asymmetry factor is determined by the formula:<br />
AF = 100 (A r / A t )<br />
where A r is the area of the basin to the right of the trunk stream that is facing downstream<br />
and A t is the total area of the drainage basin. The asymmetry factor (AF) for most stream<br />
54
networks that formed and maintained flow in steady settings is 50. Since the asymmetry<br />
factor is susceptible to any tilting perpendicular at the trunk of the stream, any AF values<br />
greater or less than 50 indicate the possibility of tilting. Any drainage basin with a<br />
flowing trunk stream that was subjected to a tectonic rotation will most likely have an<br />
effect on the tributaries’ lengths. Assuming the tectonic activity caused a left dipping to<br />
the drainage basin, the tributaries to the left of the main stream will be shorter compared<br />
to the ones to the right side of the stream with an asymmetry factor greater than 50, and<br />
vice versa (Hare and Gardner 1985, Keller and Pinter 2002), as shown in figure 2.2.<br />
Figure 2.2: Block diagram shows the effect of an asymmetry factor with a left side tilt on<br />
tributaries lengths (From Keller and Pinter 2002, figure 4.3, p. 125).<br />
Another quantitative index to evaluate basin asymmetry is the Transverse<br />
Topographic Symmetry Factor (T) that is defined as:<br />
T = D a / D d<br />
where D a represents the distance from the midline of the drainage basin to the midline of<br />
the active meander belt, and D d corresponds to the distance from the basin midline to the<br />
basin divide (figure 2.3). For diverse segments of valleys, the calculated T values indicate<br />
55
migration of streams perpendicular to the drainage-basin axis. Thus, the Transverse<br />
Topographic Symmetry Factor is a vector that has direction and magnitude that ranges<br />
from zero to one (T = 0 to 1), which reflects a perfect asymmetric basin or a tilted one<br />
respectively (Burbank and Anderson 2001, Cox 1994, Cox et al. 2001, Keller and Pinter<br />
2002). In case of a negligible influence by the bedrock tilting on the relocation of the<br />
stream channels, the direction of the regional migration is an indicator of the ground<br />
tilting in that similar direction. The analysis of numerous drainage basins in an area<br />
results in multiple spatially distributed T vectors, which, when averaged, define the<br />
irregular zones of basin asymmetry. The calculation of both AF and T is a quantitatively<br />
rapid method of identifying ground tilting (Cox 1994, Cox et al. 2001, Keller and Pinter<br />
2002).<br />
Figure 2.3: An example of calculating a drainage-basin transverse topographic<br />
asymmetry vector for a single stream segment (From Cox 1994, figure 3, p. 574).<br />
56
2.3.3. Stream Length-Gradient Index (SL)<br />
The Stream Length-Gradient Index (SL) is calculated along a river and used to<br />
evaluate the erosional resistance of the available rocks and relative intensity of active<br />
tectonics. The SL index has sensitivity to channel slope changes, which makes it a good<br />
evaluation tool for the relationship between potential tectonic activity, rock resistance,<br />
topography, and length of the stream (Azor et al. 2002, Hack 1973, Keller and Pinter<br />
2002, Zovoili et al. 2004), as illustrated in figure 2.4.<br />
Figure 2.4: Map showing the Stream Length-Gradient Index (SL) for the South<br />
Mountain-Oak Ridge, Ventura basin in south California (From Azor et al. 2002, figure 8,<br />
p. 750).<br />
57
The Stream Length-Gradient Index (SL) is calculated using the following<br />
formula:<br />
SL = (∆H / ∆L) L<br />
where SL is the Stream Length-Gradient Index, L is the total channel length from the<br />
midpoint of the reach -where the index is calculated- upstream to the highest point on the<br />
channel, and ∆H/∆L is the channel slope or gradient of the reach, where ∆H represents<br />
the change in elevation for a particular channel of the reach with respect to ∆L that<br />
symbolizes the length of the reach. The calculation of the SL index is typically achieved<br />
by obtaining the needed parameters that are directly measured from topographic maps<br />
(Azor et al. 2002, Hack 1973, Keller and Pinter 2002).<br />
The SL index is associated with stream power, which is a product of unit weight<br />
of water, discharge, and energy slope. Total stream power available at a particular reach<br />
of a channel is correlated to the ability of a stream to erode its bed and transport<br />
sediments. Hence, the total stream power is a significant hydrologic variable that is<br />
proportional to the slope of water surface and discharge. In addition, discharge generally<br />
correlates with upstream channel length and the energy slope is estimated by the slope of<br />
the channel bed, which is essential for forming and preserving rivers (figure 2.5). In<br />
landscape evolution, it is assumed that stream profiles adjust quite rapidly to rock<br />
resistance. Therefore, the SL index is applied to identify recent tectonic activity by<br />
recognizing high index values variations on a particular rock type. For this purpose, the<br />
SL index is generally calculated for a number of reaches along major streams that erode<br />
the area and results merged for analysis. Commonly, high SL index values are present<br />
where rivers cross hard rocks and reflect relatively high tectonic activity, while low SL<br />
58
index values indicate relatively low tectonic activity and suggest less-resistant and softer<br />
rock types (Hack 1973, Keller and Pinter 2002).<br />
Figure 2.5: Diagram shows the process of calculating the Stream Length-Gradient Index<br />
(SL) for a given creek (From Keller and Pinter 2002, figure, 4.6, p. 128).<br />
2.3.4. Triangular Facets Index (Pf)<br />
The topography of the mountain fronts is affected by factors such as the relative<br />
rates of faulting, erosion and deposition that determine its evolution. Rivers that flow<br />
from uplifted footwall across faults have the tendency to dissect and divide mountain<br />
fronts; on the other hand, active faulting tends to reshape their linear characters. For<br />
example, simple block uplift with the existence of two sloping sides bordered with faults<br />
will produce regularly spaced, similarly sized, and shaped basins on each side that are<br />
characterized by valleys with wide basins and narrow throats -referred to as “wine glass”-<br />
59
as they pass across the active range front. In addition, such uplift will also create a linear<br />
rang front, large triangular facets, and small piedmont fans. Therefore, the spacing of<br />
facets along range fronts reveals the evolution of drainage basins within the footwall<br />
block (Burbank and Anderson 2001, Mayer 1986), as shown in figure 2.6.<br />
Figure 2.6: (A) Rapid block uplift produces linear range front, large facets, and small<br />
fans. (B) Slow deformation cause by uplift produces irregular range front, dissected<br />
facets, and large fans (From Burbank and Anderson 2001, figure 10.1, p. 202).<br />
The actual spacing of the basins relies on their shape being circular or elongated.<br />
The spacing can be measured as the ratio (i.e. index) between the basins mean length -<br />
which is the mean distance from the main drainage divide to the mountain front- to the<br />
mean spacing of the mouths of the basins along the range front. Thus, circular basins will<br />
create broader triangular facets, while more elongated basins will produce smaller and<br />
60
more closely spaced facets (Burbank and Anderson 2001, Mayer 1986, 1990), as shown<br />
in figure 2.7. Tectonically active fault blocks will usually have higher index values that<br />
are characterized by shorter facets, elongated basins with short drainages and more<br />
closely spaced rivers. Less active tectonic fault blocks which usually are associated with<br />
older mountains, on the other hand, are distinguished by longer facets, circular basins and<br />
irregular widely-spaced rivers that show low index values. Hence, the Triangular Facets<br />
Index (Pf) is a good indicator of tectonic activity (Burbank and Anderson 2001).<br />
Figure 2.7: Circular and elongated basins (From Burbank and Anderson 2001, figure<br />
10.2, p. 203).<br />
Triangular facets are interpreted as variably degraded remnants of fault-generated<br />
footwall scarps where the degraded scarp defines the height of the facet, and the spacing<br />
of drainages incised into the footwall defines the facet width (Wallace 1978). Usually, the<br />
apex of the triangular facet is the crest of the divide between dissected drainage basins<br />
and the base corresponds to the faulted mountain front (Yeats 1997). Accordingly, the<br />
older triangular facets (i.e. first generation facets) are located away from the active<br />
mountain front, whereas the younger facets (i.e. second generation facets) are positioned<br />
more closely to the active mountain fronts (Zovoili et al. 2004), as illustrated is figure<br />
2.8.<br />
61
Figure 2.8: Location of older and younger triangular facets to mountain fronts (Modified<br />
from Zovoili et al. 2004, figure 6, p. 1720).<br />
2.3.5. Mountain front sinuosity (S mf )<br />
Mountain Front Sinuosity, a widely used geomorphic measure of seismic activity,<br />
simply reflects the balance between the tendency of uplift to maintain a fairly straight<br />
front and erosion caused by streams that tend to generate irregularities in the front over<br />
time creating a sinuous topographic structure. The degree of erosional modification of<br />
tectonic structures is measured by the mountain front sinuosity index (Bull 1977a, 1978,<br />
Bull and McFadden 1977, Keller and Pinter 2002, Rockwell et al. 1984, Silva et al. 2003,<br />
Wells et al. 1988). Mountain front sinuosity (S mf ) is defined as the ratio between (L mf ) the<br />
length of the mountain front along its base at the distinct break in slope and (L s ) the<br />
straight line length of the whole mountain front (Bull 1977b, 1978, Bull and McFadden<br />
1977, Keller and Pinter 2002) and is expressed in the formula:<br />
S mf = L mf / L s<br />
where S mf is the mountain front sinuosity index, L mf is the length along the edge of the<br />
mountain-piedmont junction, and L s is the overall length of the mountain front.<br />
62
Typically, lower values of S mf indicate active uplift processes, while higher values signify<br />
relatively less tectonic activity (Bull 1977b, 1978, Bull and McFadden 1977, Burbank<br />
and Anderson 2001, Keller and Pinter 2002, Wells et al. 1988) (figures 2.9 and 2.10).<br />
Figure 2.9: Calculating mountain front sinuosity (S mf ) index (Modified from Keller and<br />
Pinter 2002, figure 4.14, p. 137).<br />
Figure 2.10: Mountain front sinuosity (S mf ) index (Modified from Burbank and Anderson<br />
2001, figure 10.5, p. 205).<br />
63
The sinuosity (S mf ) values can be calculated from topographic maps or aerial<br />
photographs. Because S mf values are scale dependent, it is more useful to calculate them<br />
using larger scales that accentuate the irregularity of the mountain fronts. Lower values of<br />
S mf index indicate relatively active mountain fronts, while higher values signify a<br />
relatively moderate to less active (inactive) mountain fronts (Bull 1977b, 1978, Bull and<br />
McFadden 1977, Burbank and Anderson 2001, Keller and Pinter 2002).<br />
2.3.5.1. Choosing mountain fronts<br />
Both L mf and L s are measured manually in the same units as the topographic map<br />
scale (e.g. meters, feet, etc.) then fed into the equation to obtain results, thus the S mf index<br />
is unitless (Bull 1977a, 1978, 1984, Bull and McFadden 1977, Keller and Pinter 2002,<br />
Rockwell et al. 1984, Silva et al. 2003, Wells et al. 1988).<br />
Mountain fronts are defined as major fault-bounded topographic escarpments with<br />
measurable relief exceeding one contour interval of 20m (Wells et al. 1988). Mountain<br />
fronts can be calculated as one front divided into segments of approximately 1Km long<br />
(Azor et al. 2002) or as several continuous fronts of various lengths (Bull 1978, 1984,<br />
Silva et al. 2003, Wells et al. 1988). The latter approach has been adopted in this research<br />
since it is widely used and is more suitable to the current study area. According to Wells<br />
et al. (1988) and based on the method produced by Bull (1978, 1984), longer mountain<br />
fronts are subdivided into discrete segments with generally similar geologic and<br />
physiographic characteristics, based on one or more of the following criteria: (1)<br />
Intersection with cross-cutting drainages large in scale relative to the front, (2) Abrupt<br />
deflections in mountain front orientation, (3) Abrupt changes in lithology, and (4) Abrupt<br />
64
changes in the main geomorphic characteristics of a mountain front relative to adjacent<br />
front segments such as relief, steepness, or dissection (Wells et al. 1988).<br />
2.3.6. Valley floor width to valley height ratio (V f )<br />
The other important stability index is the ratio of valley floor width to valley<br />
height (V f ). This index reflects the differences between the V-shaped valleys downcutting<br />
in response to active uplift, where the stream is governed by the influence of a base level<br />
fall at some point downstream that indicates a relatively high tectonic activity, and the U-<br />
shaped broad-floored valleys with principally lateral erosion into the adjacent hillslopes<br />
in response to relative base-level stability or tectonic quiescence that signifies a relatively<br />
low tectonic activity. Therefore, this index uses one vertical and one horizontal<br />
dimension at a given point along the stream in the erosional system. The ratio of valley<br />
floor width to valley height is defined as:<br />
V<br />
f<br />
2V<br />
fw<br />
=<br />
[( E − E ) + ( E − E )]<br />
ld sc rd sc<br />
where V fw is the width of the valley floor, E sc is the elevation of the valley floor or stream<br />
channel, and E ld and E rd are the elevations of the left and right valley divides respectively,<br />
as shown in figures 2.11 and 2.12. Similar to the S mf index, lower values of the V f index<br />
indicate relatively active mountain fronts and reflect deep valleys with active incision<br />
related to uplift, whereas higher V f index values are associated with relatively moderate<br />
to less active mountain fronts that represent low uplift rates (Bull 1977a, 1978, Bull and<br />
McFadden 1977, Burbank and Anderson 2001, Keller and Pinter 2002, Rockwell et al.<br />
1984, Silva et al. 2003, Wells et al. 1988).<br />
65
Figure 2.11: Calculating valley floor width to height ratio (V f ) (From Keller and Pinter<br />
2002, figure 4.15, p. 139).<br />
Figure 2.12: Valley floor width to height ratio (V f ) (From Burbank and Anderson 2001,<br />
figure 10.6, p. 205).<br />
2.3.6.1. Choosing valley profiles<br />
Similar to the S mf index, all V f index measurements are usually obtained from<br />
topographic maps and aerial photographs (Bull 1977a, 1978, 1984, Bull and McFadden<br />
1977, Keller and Pinter 2002, Rockwell et al. 1984, Silva et al. 2003, Wells et al. 1988).<br />
The location of the cross-valley (i.e. valley profile) transects within a drainage basin<br />
affect the values of V f . Valley floors tend to become gradually narrower upstream from<br />
the mountain front and for a given stream the values of V f ratios tend to become<br />
increasingly larger downstream from the headwaters (Bull and McFadden 1977). In<br />
66
addition, the values of V f may also vary widely among streams with different drainage<br />
basin areas, discharge, and underlying bedrock lithology (Wells et al. 1988).<br />
Consequently, each study area will dictates its own valley profile measurement<br />
distance from a given mountain front based on its distinctive geomorphology and the<br />
geospatial distribution of valleys. The V f measurements were taken at a distance of about<br />
200m from mountain fronts (Zovoili et al. 2004), 250 m upstream from the mountain<br />
front (Silva et al. 2003), at a distance of 0.1 of the drainage basin length (Rockwell et al.<br />
1984), and approximately upstream at a distance of 1Km from the mountain front (Bull<br />
and McFadden 1977).<br />
Both S mf and V f values have been used to evaluate the relative degree of tectonic<br />
activity of related mountain fronts (Bull and McFadden 1977, Keller and Pinter 2002,<br />
Silva et al. 2003). However, it is very important to specify that only the combination<br />
between S mf and V f indices, especially in arid to semiarid regions are able to provide<br />
semi-quantitative information of the relative degree of tectonic activity of the examined<br />
mountain fronts and assigning them to different tectonic activity classes (Bull and<br />
McFadden 1977, Silva et al. 2003). Therefore, in this research both of these geomorphic<br />
indices were used.<br />
2.4. Satellite imagery and digital elevation models<br />
The main focus in this research is to calculate these two tectonic geomorphic<br />
indices, namely mountain front sinuosity and the valley floor width to valley height ratio,<br />
to indicate the relative seismic activity levels of the mountain fronts in JDTZ. The<br />
calculation of measurements requires elevation data that is obtainable using remote<br />
67
sensing imagery and digital elevation models (DEMs) of the study area as input layers<br />
which will be integrated using geographic information system (GIS).<br />
In previous studies conducted in different countries, the values of S mf and V f were<br />
calculated manually from topographic and geomorphological maps and aerial<br />
photographs of various scales (chapter 2, section 2.6). The best topographic maps of the<br />
JDTZ are at a scale of 1:50,000 with 20m contour intervals (figure 2.13). Producing<br />
DEMs from digitized topographic maps is time consuming and produces less-accurate<br />
results than digital topographic maps and satellite derived DEMs (Toutin and Cheng<br />
2001). Therefore, using available commercial DEMs data generated from satellite data is<br />
more convenient and has better resolution.<br />
2.4.1. Digital Elevation Models<br />
Digital elevation models offer the most common methods for extracting vital<br />
elevation and topographic information. DEMs are increasingly used for visual analysis of<br />
topography, landscapes and landforms, in addition to modeling of surface processes<br />
(Hirano et al 2003, Kamp et al. 2003, 2005, Welch 1990). Currently, DEMs have been<br />
the main source for the extraction of different geomorphological and topographic features<br />
depending on altitude and its spatial distribution and variation (Felicísimo 1994). Digital<br />
Elevation Model (DEM), Digital Elevation Data (DED), Digital Terrain Data (DTD)<br />
(Campbell 2002), or Digital Terrain Model (DTM) all include various arrangements of<br />
individual points of x (east-west direction) and y (north-south direction) coordinates of<br />
horizontal geographic locations. Z is the vertical elevation value that is relative to a given<br />
datum for a set of x, y points (Bernhardsen 1999, Bolstad and Stowe 1994, Welch 1990).<br />
They consist of samples array of elevations for a number of ground positions at equally-<br />
68
spaced intervals (USGS 1990). DEM provides a digital representation in threedimensions<br />
of a portion of Earth’s terrain. The resolution of DEMs depends on scale and<br />
resolution of the data source (digital satellite images, aerial photographs) and the spatial<br />
resolution (i.e. grid spacing) of the data samples, as well as other variables like data<br />
structure and algorithms used during the extraction process (Campbell 2002, Cuartero et<br />
al. 2004, Sabins 1997, USGS 1990).<br />
DEMs are most commonly prepared in raster data structure, which are compatible<br />
with remotely sensed data. They are represented in an array of equally spaced grids<br />
having values of the topographic elevation observed and recorded of the earth’s surface.<br />
It is similar to any remote sensing data except that each pixel shows an elevation<br />
measurement in the center of the pixel instead of brightness values (i.e. digital numbers<br />
or DNs). Using this format makes the process of manipulations, classification, analysis,<br />
and display of DEMs similar to that of remote sensing imagery (Campbell 2002). The<br />
form of surface model used for this entire study is that of the Digital Elevation Model<br />
(DEM). Although the term is used inconsistently in the literature (Burrough 1986, Weibel<br />
and Heller 1991) it is defined here consistently with the terms of Burrough (1986), as a<br />
regular gridded matrix representation of the continuous variation of relief over space<br />
(Wood 1996).<br />
69
Figure 2.13: The Aqaba 1:50,000-scale topographic map with 20m intervals. Produced by<br />
the Unites States Army, Sheet 3049 III, Series K737.<br />
70
In the last decade several developments have been introduced to satellite sensors<br />
to produce data for digital elevation model generation. Nowadays many satellites provide<br />
stereo images with high potential of producing DEMs that can be integrated in<br />
visualization software or GIS environments with available geodata and cartographic<br />
information (i.e. existing vector data) for landscape and geomorphic analysis (Poli et al.<br />
2005). However DEMs of usable details are still not available for much of the Earth, high<br />
accuracy determination and visualization of topography of the Earth’s surface is still very<br />
essential for local and national level environmental applications (Chrysoulakis et al.<br />
2004).<br />
The use of three-dimensional terrain modeling in GIS applications was made<br />
possible by the advancement in computer and database technology. The primary<br />
requirement for such application is using a DEM of the terrain within the region of<br />
interest. When combines with satellite images and GIS coverages, a DEM becomes more<br />
useful in terrain visualization and geomorphic terrain analyses (Welch 1990).<br />
The accuracy of DEMs depends on the level of detail of the source and the grid<br />
spacing used to sample the source. The scale of the source material is the main limiting<br />
factor for the level of detail of the source. DEMs are classified into three levels of quality<br />
that characterizes the model’s accuracy (USGS 1990, 1997-1998): (1) Level-1 DEMs are<br />
the standard format elevation datasets. They have the desired accuracy standards of 7m<br />
vertical root mean square error (RMSE) that doesn’t exceed the maximum 15m RMSE,<br />
(2) Level-2 DEMs are elevation datasets that have been processed and smoothed for<br />
consistency and edited to remove systematic errors. The maximum vertical RMSE is onehalf<br />
contour interval with no errors greater than one contour interval, and (3) Level-3<br />
71
DEMs are elevation datasets derived from digital line graph (DLG) data using selected<br />
elements from hypsographic and hydrologic data. The maximum vertical RMSE is onethird<br />
contour interval with no errors greater than two-third of the contour interval.<br />
2.5. Advanced Spaceborne Thermal Emission and Reflection Radiometer Satellite<br />
Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is<br />
an advanced multispectral imaging satellite, boarded on Earth Observing System EOS-<br />
AM1 platform (platform altitude of 705km) that was launched on board NASA’s Terra<br />
spacecraft in December, 1999 and placed in orbit in February 2000. ASTER is an alongtrack<br />
imager with a circular, near polar orbit (to increase the ground coverage), low<br />
inclination satellites for long-term global observations of the land surface, biosphere,<br />
solid Earth, atmosphere, and oceans at an altitude of 705km. The orbit is sunsynchronous<br />
with an equatorial crossing at local solar time of 10:30am, returning to the<br />
same orbit every 16 days. It has two visible bands, seven IR bands, and five thermal IR<br />
bands. The spatial resolution varies with wavelengths, 15m in the visible and the nearinfrared<br />
(VNIR), 30m in the short wave infrared (SWIR), and 90m in the thermal infrared<br />
(TIR). It is also equipped with off-nadir backward-viewing sensor pointing feature that<br />
has the capability to produce stereo images and in turn generate a high resolution DEMs<br />
(Abrams et al. 2003, Abrams and Hook 1995, 2002, ASTER websites, Childs 2003,<br />
Fujisada 1994, 1998, Fujisada et al. 1998, 2001, Kamp et al. 2003, 2005, Lang et al.<br />
1996, Selby 2003, Tokunaga et al. 1996, Toutin 2001, Toutin and Cheng 2001,<br />
Yamaguchi et al. 1998).<br />
All ASTER bands are designed to collect data over a swath (i.e. ground resolution<br />
cell) of 60km x 60km that requires nine seconds for each scene, and approximately 60-<br />
72
seconds for a stereo pair (Fujisada 1994, Lang et al. 1996). However, the data coverage is<br />
restricted to about 650-scenes per day that are processed to Level-1A; of these, about 150<br />
are processed to Level-1B, working under a limited 8% duty cycle (i.e. 8 minutes/orbit)<br />
and priority data acquirement with a global coverage between 85ºN and 85ºS (Abrams et<br />
al. 2003, Abrams and Hook 1995, 2002, ASTER websites, Childs 2003, Fujisada 1994,<br />
1998, Fujisada et al. 1998, 2001, Lang et al. 1996, Lang and Welch 1999, Tokunaga et al.<br />
1996, Toutin 2001, Toutin and Cheng 2001, Yamaguchi et al. 1998), as shown in figure<br />
2.14.<br />
Figure 2.14: Flat map shows ASTER DEM global coverage of January 31, 2004.<br />
2.5.1. ASTER data types<br />
The ASTER instrument has two types of data levels, Lavel-1A and Level-1B data.<br />
Level-1A data is basically defined as reconstructed, unprocessed instrument data at full<br />
resolution. Consequently, the Level-1A data consist of the image data, the radiometric<br />
coefficients, the geometric coefficients, and other supplementary data without applying<br />
73
any of the coefficients to preserve the original data values. The L1A data is used as<br />
source data to generate DEM products because of the many useful instrument parameters<br />
and information that are incorporated inside them. In addition, due to the maintained<br />
ancillary data which include the spacecraft position or the geometric correction table that<br />
contains the latitudes and longitudes of the collected pixels, high quality DEM data<br />
products can be generated (Abrams et al. 2003, Abrams and Hook 2002, Fujisada 1998,<br />
Fujisada et al. 2001, Yamaguchi et al. 1998).<br />
Alternatively, Level-1B data have no ancillary data, instrument geometric<br />
parameters, and the spacecraft information. The L1B data are normally generated<br />
applying these coefficients for radiometric calibration and geometric resampling. The<br />
L1B data product is produces, by default, in the UTM projection, in swath orientation,<br />
and Cubic Convolution resampling. However, the georeferenced and georectified L1B<br />
data is still able to produce practical quality DEM products for ASTER individual scenes<br />
(Abrams et al. 2003, Abrams and Hook 2002, Fujisada 1998, Fujisada et al. 2001, Poli et<br />
al. 2005, Yamaguchi et al. 1998). The data structure of an ASTER L1B data product is<br />
illustrated in figure 2.15.<br />
2.6. Previous studies in morphometric analysis<br />
In this section, a number of studies utilizing geomorphological indices as a tool<br />
for tectonic investigation will be described. Starting with the early studies that introduced<br />
quantitative analysis to geomorphology and ending with the most recent.<br />
The earliest application of geomorphology to the assessment of tectonic stability<br />
began with Bull and McFadden (1977). In their research conducted at the north and south<br />
ends of the Garlock fault in the Mojave Desert in California, the researchers employed<br />
74
S mf and V f index analysis to determine the Quaternary tectonic activity of the area. Based<br />
on the sinuosity values the tectonic activity of the area was classified into three classes.<br />
The area north of the Garlock faults has relatively low values of S mf index, while the area<br />
north of the fault shows a relatively high S mf index values. A transitional area in the<br />
central part of the northern area nearby the Garlock fault shows relatively high values of<br />
S mf index. Tectonic indices were calculated using elevation data obtained directly from<br />
aerial photographs, 1:62,000 scale topographic maps, and 1:250,000 topographic and<br />
geologic maps (Bull and McFadden 1977).<br />
Figure 2.15: Data structure of ASTER Level-1B granule (From Abrams et al. 2003.<br />
figure 8, p. 22).<br />
75
This study concluded that active tectonic terrains (class 1) are characterized by<br />
unentrenched alluvial fans, elongated drainage basins with narrow valley floors and steep<br />
hillslopes even in soft rock types, S mf index values of 1.0 to 1.6, and V f index values of<br />
0.05 to 0.9. Moderate to slightly active tectonism terrains (class 2) are differentiated by<br />
entrenched alluvial fans, large drainage basins that are more circular than class 1 basins,<br />
steep hillslopes, valley floors that are wider than their floodplains, S mf index values<br />
ranges 1.4 to 3.0, and V f index values of 0.5 to 2.0. The tectonically inactive terrains<br />
(class 3) are distinguished by pedimented mountain fronts and embayments, steep<br />
hillslope only on hard rock types, few large integrated stream systems in the mountains,<br />
S mf index values of 1.8 to more than 5, and V f index values greater than 2 (Bull and<br />
McFadden 1977).<br />
In a similar study conducted by Bull (1978) at the south front of the San Gabriel<br />
Mountains in California, geomorphic indices were calculated using 1:24,000-scale<br />
topographic maps with contour intervals ranging from 10 to 40 feet. This study concluded<br />
similar results to the north and south of the Garlock fault research and mountain fronts<br />
were represent the three tectonic activity classes (Bull 1978).<br />
In a parallel study, the mountain fronts and alluvial fans of the Ventura area in<br />
California were analyzed using S mf and V f indices (Rockwell et al. 1984). Eight range<br />
fronts were defined in the study area based on geographic location, geomorphic<br />
expression, and presence of known active faults and folds. This study yields two tectonic<br />
activity groups; group (1) has very active fronts while group (2) is associated with less<br />
active tectonism. The very active tectonism fronts (groups 1) are associated with<br />
faults/folds that were uplifted and tilted basinward generating a relatively large alluvial<br />
76
fans for given basin areas. The Less active tectonism fronts (group 2), on the other hand,<br />
has relatively small alluvial fans that are more constrained in their depositional areas. The<br />
alluvial fans with larger fan areas are associated with mountain fronts having higher rated<br />
of tectonic activity (Rockwell et al. 1984).<br />
The relatively active fronts produced lower S mf and V f values in comparison with<br />
the less active fronts that show higher values of both S mf and V f . The V f index values<br />
varies from 0.43 to 1.91, while the tectonically active fronts S mf index values ranging<br />
1.01 to 2.72 indicating an active uplift in the study area. The geomorphic analysis results<br />
indicated that tectonically active fronts have low S mf range from 1.01 to 1.34 with an<br />
average of 1.14, while the less active fronts have sinuosities that range from 1.57 to 2.72<br />
with an average of 2.04. The study concluded that both S mf and V f indices are useful<br />
indicators of relatively tectonic activity in the Ventura area. All Indices were calculated<br />
from the United States Geological Survey 7.5-minute topographic map (1:24,000-scale)<br />
with 40 foot contour intervals (Rockwell et al. 1984).<br />
Another study conducted by Wells et al. (1988) using tectonic geomorphology<br />
indices as an indicator to relative tectonic activity in the Pacific coastal mountains and<br />
piedmonts of Costa Rica. The research utilized morphometric analyses of 100 mountain<br />
fronts and abundant river long-profiles along with field studies and radiometric dating<br />
over two study areas (regions I and II) located within the subduction zone between the<br />
Cocos and the Caribbean tectonic plates (Wells et al. 1988).<br />
The geomorphic analysis results of the two regions have shown differences in<br />
values based on the region. Region I, located to the northern coastal areas within the<br />
transitional plate boundary zone, where region II is located in the southern segment that<br />
77
indicates an occurrence of high degree of tectonic activity on-shore opposite to the<br />
subduction seismic ridge. The S mf index values of region I range from 1.0 to 3.1<br />
indicating relatively high sinuosity values of mountain fronts that are more sinuous and<br />
dissected. On the other hand, region II S mf index results range from 1.0 to 2.2 that signify<br />
relatively low sinuosity values of mountain fronts -compared to region I- that are less<br />
sinuous and dissected due to their location in the interior mountainous regions. In<br />
general, low mean values of mountain front sinuosity were clustered around 1.2 to 1.5 in<br />
the more tectonically active region I and its subregions, while the mean values were<br />
between 1.1 to 1.5 in the less active region II and its subregions. On the other hand, the<br />
V f index values ranging from 1.1 to 32, with typical values of 0.2 to 7. Individual stream<br />
in upstream regions (less active) show low V f values of less than 1 to 2. Where individual<br />
streams in downstream regions (more active) show higher V f ratios. The wide-floored<br />
valleys were located one or more kilometers from the escarpment and have high Vf<br />
values generally more than 2, where V-shaped valleys associated with development of<br />
deep and narrow canyons close or immediately upstream from the intersection with the<br />
fronts indicated low V f values generally less than 1. The entire geomorphic<br />
measurements were acquired from 1:50,000 scale topographic map with 20m contour<br />
intervals (Wells et al. 1988).<br />
This study emphasizes the practicality of geomorphic analysis for detecting<br />
spatial variation in plate tectonic framework within convergent tectonic plate boundaries<br />
(e.g. subduction ridges). Such morphometric analysis being normally utilized in arid and<br />
semiarid regions of compressional and extensional terrains along mountain fronts would<br />
yields satisfactory results when used in the coastal regions (Wells et al. 1988).<br />
78
In an attempt to provide information concerning the active fold growth in the<br />
South mountain-Oak Ridge, a tectonic geomorphic analysis study using several<br />
geomorphic indices was carried out by Azor et al. (2002). The South mountain-Oak<br />
Ridge near Ventura basin, southern California, is an asymmetric anticlinal uplift above<br />
the active and buried Oak Ridge reverse fault. The shortening along the fault started to<br />
accumulate since the Quaternary time and is responsible for the growth and current<br />
topography of the westernmost 15km of the ridge during the past 0.5Myr (Azor et al.<br />
2002).<br />
To quantify the geomorphology of the South Mountain-Oak Ridge, several<br />
geomorphic indices were involved in this research including stream length-gradient index<br />
(SL), mountain front sinuosity (S mf ), ratio of valley floor width to valley height (V f ), and<br />
hypsometric integral index (Hi). The S mf index values roughly decreased from<br />
approximately 2 to 1 along the northern slope of the anticlinal ridge towards the<br />
westernmost 10km of observed surface folding indicating a lower S mf values and active<br />
uplifting. In general, V f index values along the northern side of the ridge decreased<br />
westward from about 1.5 to 0.5 indicating rapid uplift and valley incision. Values of the<br />
Hi index along the northern side of the ridge increase considerably from roughly 0.35 to<br />
0.4 with a maximum of around 0.55. In addition, the northern, eroded fold scarp of the<br />
ridge represents were relatively high SL index values, which is a pattern consistent with<br />
the existence of active and rapid slip on the Oak Ridge fault. Evidently, the overall results<br />
obtained from geomorphic indices of the western segment of the South mountain-Oak<br />
Ridge emphasize the westward lateral growth of the underlying anticline. In conclusion,<br />
79
the tectonic geomorphic analysis of the ridge confirms the usefulness of geomorphic<br />
indices of active tectonics to identify and evaluate active fold growth (Azor et al. 2002).<br />
Recent research was conducted by Silva et al. (2003) to determine the tectonic<br />
activity over 17 different mountain fronts in southeastern Spain. The fronts are<br />
distributed along the Valencia Trough and the Eastern Betic Shear Zone (EBSZ), which<br />
are the two most prominent crustal-scale structures of the Mediterranean sector of Spain.<br />
Mountain front sinuosity values were calculated using 1:50,000-scale topographic and<br />
geomorphic maps with four contour intervals (100m height) produced by the authors of<br />
the study area, while the valley floor width/height ratio values were calculated from<br />
1:25,000-scale topographic maps (Silva et al. 2003).<br />
The geomorphic index values for the mountain fronts under study were classified<br />
into three tectonic classes and associated with an estimate of tectonic uplift rates. Class 1<br />
indicating tectonically active fronts with S mf index values ranging from 1.17 to 1.53<br />
(mean values = 1.4) and V f index values < 0.5. Class 2 indicating moderately active<br />
fronts with S mf index values ranging 1.8 to 2.30 and V f index values ranging 0.3 to 0.8.<br />
Finally, class 3 indicating inactive fronts with S mf values ranging 2.8 to 3.5 and V f index<br />
values that is > 0.7 and ranging 0.8 to 1.2 (Silva et al. 2003).<br />
After the application of S mf and V f analysis over the 17 mountain front in SE<br />
Spain, the study concluded the occurrence of different morphometric properties for<br />
different tectonic landscapes (i.e. tectonic classes) and faulting styles that could only be<br />
practically distinguished by means of statistical analysis using S mf /V f regression. These<br />
tectonic classes could be linked to the available uplift rates from the last 100kyr in both<br />
regions under study in SE Spain mountain fronts for better understanding of their tectonic<br />
80
activity. As a result, each tectonic activity class was assigned uplift rates and recurrence<br />
intervals of earthquake activities as follow, class 1 an uplift rate of > 0.15 to 0.08 m/kyr,<br />
class 2 an uplift rate of 0.07 to 0.03 m/kyr, and class 3 an uplift rate of < 0.03 m/kyr<br />
(Silva et al. 2003).<br />
Another recent study was undertaken by Zovoili et al. (2004) to study the tectonic<br />
geomorphology of escarpments of two faults located in mainland Greece. The<br />
Kompotades and the Nea Anchialos faults in the Sperchios and South Thessaly rift zones,<br />
respectively, were studied using morphometric analysis. Three geomorphic indices were<br />
applied namely mountain front sinuosity (S mf ), the valley floor width to valley height<br />
ration (V f ), and the stream length-gradient (SL) index (Zovoili et al. 2004).<br />
In order to gather more information about the tectonic activitie of the two faults,<br />
the historical seismicity of the region was taken into consideration. The V f index values<br />
ranged between 0.4 to 1.2, with more significant values close to 0.7, implying high uplift<br />
rates. While the S mf index values concentrated around ≈ 1 demonstrating relatively high<br />
tectonic activity in both faults that decreased toward the west. On the other hand, the SL<br />
index, which is more sensitive to non-tectonic processes such as rock resistance and<br />
stream length were found to be less indicative of tectonic activity (Zovoili et al. 2004).<br />
The recurrence interval of the Nea Anchialos fault according to the historical<br />
seismicity is about 1500 years and in case of the Kompotades fault the interval is more<br />
than 2500. Given that both faults have the same V f index values, this suggest that the Vf<br />
index seems to be sensitive for longer periods than 2500 years. This study concluded that<br />
the combined values of the S mf , V f , and SL indices calculations indicate that both faults<br />
81
are very active and they belong to the first class (i.e. class 1) of tectonic activity (Zovoili<br />
et al. 2004).<br />
Several studies in different places in the world have utilized tectonic geomorphic<br />
analysis approach to investigate tectonic activities in multiple geomorphic and geologic<br />
settings. For example, researches took place in the Gorajec river basin in Roztocze in SE<br />
Poland (Brzezińska-Wójcik et al. 2002), eastern California shear zone and parts of the<br />
basin and range located in eastern Mojave Desert (Dudash et al. 2003), southern<br />
interpolate Shillong Plateau in Bangladesh/India (Biswas and Grasemann 2005), the SW<br />
border of Sierra Nevada in Granada, Spain (El-Hamdouni et al. 2006), and the Alborz-<br />
Central Iran border zone, from the east of Varamin of the east of Semnan (Arian and<br />
Faranak 2006) all verified the usefulness of tectonic geomorphic index analyses in<br />
determining and classifying relative tectonic activity along mountain fronts and river<br />
basins.<br />
2.7. Summary<br />
Detailed quantitative measurements of landforms are able to provide essential<br />
information to objectively compare and calculate geomorphic indices that are practical<br />
for identifying the characteristics of a particular area such as its level of tectonic activity.<br />
Therefore, combined evaluation of several indices would seemingly develop a system of<br />
relative tectonic activity classes. Generally, the classification of areas being very active,<br />
moderately active, and less active (inactive) is useful in locating active structures and the<br />
calculation of active tectonic processes rates (Keller and Pinter 2002). A summary of the<br />
S mf and V f indices ranges of selected significant studies are listed in table (2.1).<br />
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Literature Tectonic Classes S mf ranges V f ranges<br />
1 1.0 - 1.6 0.05 - 0.9<br />
Bull & McFadden (1977)<br />
2 1.4 - 3.0 0.5 - 2.0<br />
3 1.8 - >5 >2.0<br />
Rockwell et al. (1984)<br />
Active fronts 1.01 – 1.34 (Ave. 1.14)<br />
Less active fronts 1.57 – 2.72 (Ave. 2.04)<br />
0.43 - 1.91<br />
Wells et al. (1988)<br />
More active 1.0 – 3.1 (mean 1.2 – 1.5) < 1.0, V- valley<br />
Less active 1.0 – 2.2 (mean 1.1 – 1.5) > 2.0, U- valley<br />
Azor et al. (2002) Active uplift Values Decreased ≈ 2 to 1 decreased ≈ 1.5 to 0.5<br />
1 1.17 – 1.53 (mean 1.4) < 0.5<br />
Silva et al. (2003)<br />
2 1.8 – 2.30 0.3 – 0.8<br />
3 2.8 – 3.5 > 0.7 (mostly 0.8 – 1.2)<br />
Zovoili et al. (2004) High upllifting Around 1.0 0.4 – 1.2 (significant 0.7)<br />
Table 2.1: The S mf and V f indices ranges of selected literature.<br />
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3. Chapter Three: Materials and Methods<br />
3.1. Introduction<br />
This chapter provides details of the methods and procedure used to collect the<br />
data for study. This includes the acquisition, preparation, and processing of the digital<br />
data, generating ASTER DEMs, and morphometric analyses. In addition, the digitizing of<br />
mountain front sinuosity and valley profiles over the areas that fit the geomorphic indices<br />
criterion applying the digital approach is explained. Finally, all analytical results are<br />
depicted in maps, three-dimensional images, and tables to ease the method of comparing<br />
results and extracting conclusions.<br />
3.2. The digital morphometric approach<br />
In general, all index measurements in the previous morphometric studies were<br />
manually obtained from topographic maps and aerial photographs of various scales where<br />
available. Therefore, the digital approach adopted in this study will try to replace<br />
topographic maps by digital elevation sources of the study area to calculate both S mf and<br />
V f indices. Toward this, digital elevation models (DEMs) and shaded relief maps of the<br />
study area replace topographic maps as elevation sources.<br />
Integrated layers of vector and raster data of both delineated mountain fronts and<br />
valley profiles that comprises digitized fronts and their overall lengths will operate as<br />
digital measurement tools. In addition, a three-dimensional cross section of each<br />
designated valley profile is used as an elevation reference for the right and left valley<br />
divides and its floor as well as a measurement tool to calculate each valley floor width.<br />
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3.2.1. Choosing mountain fronts<br />
In this current research, the mountain fronts were distinguished and delineated<br />
based on the presence of any intersection with large scale cross-cutting drainages.<br />
Generally, all selected mountain fronts were acknowledged as a single continuous front<br />
until they encountered major interruption by large-scale drainages or valleys. Hence, new<br />
mountain fronts start at another front that is discontinuous and/or trends in a different<br />
direction (Bull 1978).<br />
3.2.2. Choosing valley profiles<br />
In this study, the transect distance of valley profiles for determining V f values<br />
ranged between 45m to 1,200m (only two cases reached about 2,500m) upstream from<br />
the mountain fronts, and approximately parallel, for each given mountain front.<br />
Accordingly, a number of mountain fronts were associated with several valley profiles<br />
while other fronts were linked to at least one profile based on the ability of identifying<br />
pronounced valleys due to the DEM resolution and the availability of the digital data at<br />
the selected valley locations.<br />
3.3. ASTER Stereo capability<br />
The ASTER stereo subsystem that has the capabilities of generating DEMs<br />
include the nadir-looking and backward-looking telescopes that yields a base-to-height<br />
ratio (B/H) of 0.6 (Hirano et al. 2003, Lang et al. 1996, Tokunaga et al. 1996, Yamaguchi<br />
et al. 1998), which is close to ideal for generating DEMs with automated techniques for a<br />
variety of terrain conditions (Hirano et al. 2003). The visible/near-infrared (VNIR)<br />
subsystem has both nadir-looking (band 3N) and backward-looking telescopes (band 3B)<br />
pair in the near-infrared spectral band that is used for same orbit stereo imaging. The two<br />
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telescopes are designed to facilitate stereoscopic viewing capability in the along-track<br />
direction and to enable the large B/H ratio to be fixed at 0.6 (Fujisada 1998, Fujisada et<br />
al. 1998).<br />
One of the advantages of the along-track data acquisition system is that the<br />
images creating the stereopairs are obtained a few seconds apart under consistent lighting<br />
and environmental conditions, producing a stereopairs of homogeneous quality that are<br />
suitable for generating DEMs employing automated stereocorrelation techniques (Hirano<br />
et al. 2003) (figure 3.1). ASTER is capable of producing 771 digital stereopairs per day<br />
(Lang and Welch 1999, Welch et al. 1998). To produce a stereo pair image, there is about<br />
a 60-second interval between the time the ASTER nadir telescope passes over a ground<br />
location and the backward telescope (27.6° or 27.7° off nadir) records the same location<br />
on the ground path of the satellite. By that time, the satellite travels an estimated distance<br />
of 370km over the earth’s surface (ground speed is 6.7km/sec) producing the 60km stereo<br />
scene (Chrysoulakis 2004, Fujisada 1994, Hirano et al. 2003, Kamp et al. 2003, Lang et<br />
al. 1996, Lang and Welch 1999, Toutin 2001, Welch et al. 1998), as shown in figure 3.2.<br />
Figure 3.1: Simplified diagram of imaging geometry and data acquisition timing for<br />
ASTER along-track stereo image (From Welch et al. 1998, figure 2, p. 1283).<br />
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Figure 3.2: Simplified diagram of the imaging geometry for ASTER along-track stereo<br />
image “stereo configuration” (From Hirano et al. 2003, figure 1, p. 358).<br />
3.4. Obtaining ASTER imagery data<br />
The choice of satellite imagery mostly depends on the availability of data for a<br />
certain location, time, price, and the required scale of the application (Poli et al. 2005).<br />
ASTER imagery was specifically chosen in this research for four main reasons: (1) its<br />
worldwide coverage (2) the capability of generating DEMs from its stereo images, (3)<br />
high quality ground resolution of 15m which is suitable for landforms identifications, and<br />
finally (4) the affordable prices of ASTER images per scene.<br />
ASTER satellite images are available at the United States Geological Survey<br />
(USGS) website (http://glovis.usgs.gov) that easily allows browsing, purchasing, and<br />
downloading satellite data. Multiple sensors are listed as separate links enabling viewing<br />
and purchasing of scenes utilizing the USGS global visualization viewer, they can be<br />
done by visiting the desired sensor link. ASTER data are available at a separate link<br />
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(http://glovis.usgs.gov/ImgViewer/ImgViewer.html?lat=&lon=&mission=ASTER&senso<br />
r=ASTERVNIR) and scenes are provided as mosaics each show the acquisition date, its<br />
unique reference number, longitude and latitude, satellite path and row, and cloud cover<br />
percentage as illustrated in figure 3.3.<br />
Figure 3.3: The USGS global visualization viewer showing ASTER scenes of Jordan.<br />
Four ASTER Level-1B data scenes of the same swath with 14 spectral bands were<br />
purchased representing the Gulf of Aqaba (one scene), Wadi Araba (two scenes), and the<br />
Dead Sea (one scene) in Jordan. The browser allows choosing from multiple satellite<br />
platforms and scenes acquired in different years and seasons of nearly the entire world.<br />
The satellite data chosen for the study area were acquired in September 16, 2002 with a<br />
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zero percent (0%) cloud cover for the entire four scenes. The four ASTER scenes were<br />
delivered as a Pull-FTP site sent through email after ordering. The total price is 225 USD<br />
with a price of US $55 for each scene and US $5 data processing and handling (Kamp et<br />
al. 2003, 2005, Poli et al. 2005). Table 3.1 shows the area coverage of ASTER imagery of<br />
Jordan-Dead Sea Transform Zone (JDTZ) area and the type of data products (i.e.<br />
granules) and their reference numbers listed from north to south.<br />
The coordinates for all ASTER images for areas around the world are recorded in<br />
the Universal Transverse Mercator (UTM) coordinate system in meters and referenced to<br />
the World Geodetic System of 1984 (WGS-84) ellipsoid (Hirano et al. 2003, Lang et al.<br />
1995, Lang and Welch 1999, Fujisada 1998, Fujisada et al. 2001).<br />
Area coverage Data Type Granule/Product Cost<br />
The Dead Sea ASTER L1B registered SC: AST_L1B.003:2008495456 $55<br />
radiance at the sensor V003<br />
North Wadi Araba ASTER L1B registered SC: AST_L1B.003:2008495466 $55<br />
radiance at the sensor V003<br />
South Wadi Araba ASTER L1B registered SC: AST_L1B.003:2008495566 $55<br />
radiance at the sensor V003<br />
Aqaba ASTER L1B registered<br />
radiance at the sensor V003<br />
SC: AST_L1B.003:2008495567 $55<br />
Table 3.1: ASTER scenes selected to cover the JDTZ study area.<br />
3.5. Viewing ASTER data in PCI Geomatica<br />
PCI Geomatica software (Geomatica 2003) facilitates working with imagery,<br />
vectors, graphical bitmaps, and other geospatial using its Focus application. Focus is a<br />
visual environment with many useful display tools that enables viewing, editing, and<br />
enhancing remotely sensed data of a variety of satellite sensors and aerial photography.<br />
All data is stored together as the native PCIDSK file format using a single file name<br />
extension of PIX that contains all features and database tables. Moreover, the image data<br />
are stored as channels and auxiliary data are stored as segments which makes it easier for<br />
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the PCI Geomatica software application tools to perform searching, sorting, and<br />
recombining operations of such data type (Geomatica 2003).<br />
Viewing ASTER images begins with starting up Geomatica Focus from the<br />
Geomatica Toolbar (figure 3.4). To view any ASTER images, the first step would<br />
normally be to import the HDF files using Geomatica Focus into PCIFDSK then save<br />
them as *.PIX format. In Focus window, File> Utility> Import to PCIDSK. Next browse<br />
for the source file and set the options to default. Then chose the ASTER sensor<br />
instrument needed to create the image from (in this case VNIR) and click OK (figure<br />
3.5). Finally, set the output file destination path then click Import (figure 3.6).<br />
Figure 3.4: Focus is the first icon on the Geomatica Toolbar.<br />
Figure 3.5: Selecting ASTER VNIR sensor images.<br />
Figure 3.6: Import File window.<br />
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To view the final imported ASTER VNIR PIX image(s) composite in Focus<br />
window, select File> Open> and navigate to the *.PIX file location. Other methods to<br />
view the ASTER PIX image would be adding three layers of different bands to create the<br />
composite image [Layer> Add> RGB> bands 3N, 2, and 1> Finish]. Both methods will<br />
convey the same results as shown in figure 3.7.<br />
Figure 3.7: ASTER 3-2-1 color composite image of Aqaba recorded to the UTM<br />
coordinate system and referenced to WGS-84 ellipsoid.<br />
3.6. Generating ASTER DEMs<br />
In this section, the processes of generating ASTER DEMs and all associated<br />
stages such as importing/exporting and converting satellite images, creating epipolar<br />
images, generating and editing final DEMs, and photogrammetric software involved in<br />
the process are explained in details and depicted in figures. In addition, an in-depth detail<br />
91
of the process of obtaining Landsat 7 enhanced thematic mapper plus (ETM+) images<br />
and vector data to facilitate digitizing mountain fronts and related valleys to calculate the<br />
S mf and V f geomorphic index values is also explained.<br />
3.6.1. Generating and extracting DEMs from ASTER data<br />
3.6.1.1. PCI Geomatica software<br />
PCI OrthoEngine software is an efficient photogrammetric tool that handles a<br />
wide range of dataset formats with the capability to produce quality geospatial products<br />
(Geomatica 2003). OrthoEngine supports reading of ASTER data, ground control points<br />
(GCPs) collection, geometric correction, ortho-rectification, DEM generating and<br />
modeling, and either manual or automatic mosaicking. In addition, this software also has<br />
the capability to automatically generate DEMs from either aerial photographs or satellite<br />
stereoscopic sensors (Geomatica 2003, Toutin and Cheng 2001). PCI OrthoEngine<br />
software was developed at the Canada Center for Remote Sensing (CCRS), Natural<br />
Resources in Canada. Currently, this software is extensively used by the NASA EOS<br />
Land Processes Distributed Active Archive Center (DAAC) located at the USGS EROS<br />
Data Center to produce EOS Standard Product DEMs from stereo ASTER data (Toutin<br />
and Cheng 2001).<br />
In the process of DEM extraction, the selection of very important points known as<br />
tie points (TPs) is common in DEM manual processing. Usually, manual selection of<br />
points produces low quality DEMs with a lot of redundant or irrelevant information<br />
potentially being lost, which is omitted when using automated DEM extraction. The basic<br />
conditions necessary for generating an accurate DEM are: (1) using high accuracy control<br />
points, and (2) using enough tie points to guarantee error control dependability (Cuartero<br />
92
et al. 2004). Commonly, the use of accurate tie points will speed up and would result in<br />
significant enhancement of the DEM generation process (Lang and Welch 1999, Selby<br />
2003), as the quality of TPs is crucial for the final DEM quality (Kamp et al. 2003). Tie<br />
points can be chosen manually or automatically and are used to refine the relative<br />
orientations of the stereo images. This is the triangulation process and once it is complete,<br />
the DEM is created by finding conjugate points in the stereo pair in a manner similar to<br />
automatic tie point finding but much, much more dense. The tie points then guide the<br />
DEM point finder enabling it to better find DEM points (figures 3.8 and 3.27).<br />
Figure 3.8: Comparing raw images to epipolar images (From Geomatica 2003, figure 6.2,<br />
p. 69).<br />
OrthoEngine allows work with specific modules for large set of spatial data<br />
including ASTER. The influence of software is very obvious in terms of DEM results.<br />
The PCI Geomatica software includes an ASTER specific model that compensates for the<br />
shortage of orbital parameters that uses the ephemeris and attitude information recorded<br />
in the ASTER metadata which accordingly produces better-quality DEMs (Cuartero et al.<br />
2004, Geomatica 2003, Lang and Welch 1999). Basically, the ASTER satellite orbital<br />
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math model is able to compensate for the effects of varying terrain and for the distortions<br />
inherent to the camera. Such parameters include the curvature of the lens, the focal<br />
length, the perspective effects, and the camera’s position and orientation. In addition, the<br />
calculated math model calculates the camera’s position at the time when the images were<br />
taken (Geomatica 2003).<br />
In case of ASTER data products, the software uses a minimum of six tie pints (or<br />
GCPs) located in both 3N and 3B images to generate a pair of epipolar images in order to<br />
retain elevation parallax in only one direction (i.e. y-axis, N-S direction). Epipolar images<br />
are stereo pairs that are reprojected to have a common orientation and matching features<br />
between the right and left stereo images (Geomatica 2003, Selby 2003). Then an<br />
automatic image-matching procedure is used to produce the DEM through a comparison<br />
of the individual gray values of these images. This procedure utilizes a hierarchical subpixel<br />
normalized cross-correlation matching method to find the corresponding pixels in<br />
the left and tight epipolar images. The difference in location between images gives the<br />
parallax arising from the terrain relief, which is then converted to elevation values above<br />
the local mean sea level of the given datum (Geomatica 2003, Lillesand et al. 2004,<br />
Toutin and Cheng 2001). Figure 3.9 is a simplified scheme showing the algorithm for<br />
measuring height (∆h) from parallax difference in an ASTER stereopairs where B is the<br />
base and equals to X 1 . For the nadir (vertical-looking) and the aft (backward-viewing)<br />
cameras configuration, ∆h is related to the camera orientation angle (α) and the time<br />
interval (∆t) required to record both the top and the bottom of the object, which is<br />
represented by (X 1 -X 2 ) = ∆p in the nadir/aft stereopair (Lang and Welch 1999).<br />
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Figure 3.9: Measuring height from ASTER stereopair parallax difference (From Lang and<br />
Welch 1999, figure 2.0-3, p. 13).<br />
PCI Photogrammetric software uses automatic stereo image correlation approach<br />
to extract DEMs by calculating the parallax differences from ASTER 3N and 3B<br />
channels (Chrysoulakis et al. 2004, Lang and Welch 1999, Poli et al. 2005). This method<br />
is able to automatically produce relative DEMs from ASTER stereopairs in PCI<br />
OrthoEngine tool using simply tie points to adjust the images together (Chrysoulakis et<br />
al. 2004, Kamp et al. 2003). In this research both TPs and GCPs were utilized in<br />
generating epipolar stereopairs and in turn the final DEMs for the JDTZ. The use of TPs<br />
alone has the advantage of speeding up the process but the accuracy for the resulting<br />
DEM will be inferior to the one created using both GCPs and TPs. Once any TPs and<br />
95
GCPs have been collected, then a bundle adjustment operation is performed to computes<br />
a photogrammetric model using the orbital and sensor ephemeris information, plus the<br />
GCPs and TPs, so that images are located relative to each other and to the ground (Lang<br />
and Welch 1999, Selby 2003). The only difference between these points’ types is that<br />
TPs are used to match points to relate stereo images to each other, which can be<br />
calculated either manually or automatically. While GCPs are used to adjust the images to<br />
the shape and orientation of the earth’s surface which typically come from an<br />
independent source such as GPS.<br />
The process of generating DEMs using PCI Geomatica software requires the<br />
construction of a stereo pair by registering two images of the same ground area recorded<br />
from different positions in space. Any positional differences in the stereo pair that are<br />
parallel to the direction of satellite travel (i.e. parallax difference) are attributed to<br />
displacements caused by relief on the ground (figure 3.9). Relative ground elevations are<br />
determined by measuring the parallax difference in the registered images that eventually<br />
are converted to relative or absolute (if GCPs available) elevations (z-coordinate values)<br />
in the final DEM (Lang and Welch 1999). The specifications of a standard ASTER DEM<br />
data product are illustrated in figure 3.10 and table 3.2.<br />
Standard ASTER DEM Products<br />
Unit of coverage 60km x 60km ASTER Scene<br />
Format<br />
Elevations in meters; UTM; WGS-84<br />
Resolution X-Y = 15, 30m, or 90m; Z = 1m<br />
Product Name GCP Accuracy DEM Accuracy<br />
Relative DEM None 10-30m<br />
Absolute DEM 15-30m (or 5-15m) 15-50m (or 7-30m)<br />
Table 3.2: Specification for standard ASTER DEM products (Modified from Lang and<br />
Welch 1999, table 3.0-1, p. 19).<br />
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Figure 3.10: Summary of a standard ASTER DEM product generation process (Modified<br />
from Lang and Welch 1999, figure 3.0-2, p. 17).<br />
3.6.1.2. DEMs extraction process<br />
Whatever the image data are used, the main digital processing steps for DEM<br />
generation are: (1) setting-up the stereo images, (2) data extraction by image matching,<br />
(3) the 3D stereo intersection, and (4) the DEM editing (Toutin 2001). In this research,<br />
some guiding principles were followed for DEM generation that includes: (1) generating<br />
DEMs automatically, if possible, with minimal manual intervention to reduce induced<br />
inaccuracy, (2) GCPs were only exploited to match the JDTZ generated DEMs to<br />
GTOPO30 based on the satellite ephemeris data, no elevation values were used due to the<br />
lack of such data from the source, (3) coarse DEM GTOPO30 database are utilized to fix<br />
97
possible missing data within generated ASTER DEMs, and (4) DEMs of 30m grid are<br />
generated (Fujisada et al. 2001, Tokunaga et al. 1996).<br />
The extraction of ASTER DEMs process is explained in more details in the<br />
literature provided by Geomatica (2003, chapter 6) and Selby (2003). These tutorials<br />
illustrate the relative straightforward procedures of the automatically extraction of DEMs<br />
and orthorectified images from ASTER satellite imagery utilizing PCI Geomatica<br />
OrthoEngine. The output of the automatic extraction of ASTER images is orthorectified<br />
DEM and images which are automatically geocoded that can be used with other datasets<br />
and to orthorectify other images within ASTER files or other satellite images (Selby<br />
2003). The step-by-step DEM extraction methods derived from ASTER purchased<br />
images of the JDTZ study area in addition to all input options and final editing are<br />
explained in this section.<br />
All of the L1B data (and L1A data) are basically stored together with metadata in<br />
one HDF file (Abrams et al. 2003, Abrams and Hook 2002, Selby 2003). The stereo<br />
images corresponding to bands 3N and 3B are extracted from the original hierarchical<br />
data format (HDF) file in PCI Geomatica 9.1 environment. Both channels have different<br />
size due to the different detector size (Chrysoulakis et al. 2004, Fujisada 1994, Fujisada<br />
et al. 1998, Poli et al. 2005).<br />
In general, ASTER L1B VNIR subsystem dataset band 3N has 4200 (rows) x<br />
4980 (columns) pixels and band 3B has 4600 (rows) x 4980 (columns) pixels (Abrams et<br />
al. 2003). Therefore, the ground coverage in across-direction is the same, while in the<br />
along-track direction, the scene 3B covers a longer area than 3N (Poli et al. 2005). A time<br />
delay occurs between the acquisition of the backward-viewing image and the nadir<br />
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image. During this time Earth rotation displaces the image center. The VNIR subsystem<br />
automatically extracts the correct 400 pixels based on the orbit position information<br />
supplied by the EOS platform. The pixels of 400 lines on band 3B equals to about 8.7%<br />
of the whole band 3B image, plus both sides shift. The estimated 3N and 3B overlap area<br />
is approximately 85% of the image area (JPL, personal communication).<br />
For the georeferencing of all ASTER imagery the position and attitude of the<br />
sensors at the acquisition time of each image line is required. The metadata contained in<br />
the HDF file supplied this information (Poli et al. 2005).<br />
-Step One: Create a new project<br />
Initially click the OrthoEngine icon on the Geomatica 9.1 Toolbar to start<br />
OrthoEngine (figure 3.11). Creating a new project starts with opening a new file from the<br />
OrthoEngine File menu. Each ASTER scene in the study area requires a separate project,<br />
thus, four projects were created for this purpose. Then, construct a new project from the<br />
processing step drop-down menu (figure 3.12). After that, the software gives the option to<br />
read the satellite data from a variety of data storage media such as CD-ROM, hard drive,<br />
or a tape (figure 3.13). This will lead to a new window where the project information<br />
needs to be entered. After filling in the filename and the project description in the<br />
designated boxes, the next step would be choosing the math modeling method and setting<br />
up the options. The options include the high resolution satellite being used to create the<br />
DEMs from; in this case ASTER was selected (figure 3.14).<br />
Figure 3.11: OrthoEngine (4 th icon) on the Geomatica Toolbar.<br />
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Figure 3.12: Opening new project from the processing step drop-down menu.<br />
Figure 3.13: Reading satellite data from hard drive using the 3 rd icon.<br />
3.6.1.3. The math model<br />
The math model is the mathematical relationship used to correlate the pixel of the<br />
used satellite image to correct locations on the ground considering know distortions. The<br />
math model directly impacts the outcome of the final project; therefore, choosing the<br />
correct model that matches the imaging sensor is essential. The satellite orbital math<br />
modeling is a rigorous model developed to compensate for distortion cause by sensor<br />
geometry, orientation, and integration time, satellite orbital and altitude variations, earth<br />
relief, shape, and rotation, the platform position, velocity, and orientation. The ASTER<br />
math model principally calculates the position and orientation of the sensor at the time<br />
the images were taken. The accuracy of the ASTER satellite orbital math model is about<br />
one-third of a pixel in the VNIR satellite images (Geomatica 2003).<br />
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Figure 3.14: Project Information window including project name and setting the<br />
mathematical model method and the satellite options.<br />
Afterward, the output projection for the output DEM and orthoimages should be<br />
set as a first step (Geomatica 2003, Selby 2003) to UTM zone-36: 30E to 36E, Row: R-<br />
24N to 32N, and WGS-84 ellipsoid (D-000-Global Datum Definition or Ellipsoid E012).<br />
Since ASTER VNIR data are used to generate the DEMs, the output pixels spacing<br />
should match the used 3N and 3B bands which is set to 15m. In the presence of GCPs, it<br />
is recommended to set their projections based on the output file, as shown in figures 3.15<br />
to 3.19.<br />
Figure 3.15: Setting project projection to UTM.<br />
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Figure 3.16: Setting the UTM zones.<br />
Figure 3.17: Setting the UTM rows.<br />
Figure 3.18: Setting Earth Model (Ellipsoid).<br />
Figure 3.19: Setting GCPs to match the output file projection.<br />
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Finally, the project is ready to read the raw ASTER data HDF files in order to<br />
process the stereo images and create the DEMs (figure 3.20). Select both 3N and 3B<br />
bands to be read and create 3N.pix and 3B.pix and their resultant report files 3N.rpt and<br />
3B.rpt, respectively. Then provide an output filename for each band. It is important to<br />
read band 3N first as one file then band 3B as another. The reason for not reading them<br />
into a single file is due to the different pixel/line size of band 3B to band 3N (Selby<br />
2003).<br />
Figure 3.20: Reading row ASTER data HDF files from the hard drive.<br />
-Step Two: Collecting ground control points and tie points<br />
Selecting the right number and the best ground control points locations directly<br />
affect the satellite orbital math model and eventually the accuracy and quality of the<br />
generated DEMs. It is essential to choose features that are recognized accurately at the<br />
resolution of the raw image. To improve the accuracy of the output DEMs generated<br />
from ASTER images the minimum GCPs recommended are six points per image,<br />
however, collecting more than the minimum number of points uniformly throughout the<br />
images ensure the overall DEMs accuracy (Geomatica 2003).<br />
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All images have 121, evenly spaced GCPs with x and y locations on the ground.<br />
However, the z-values are not provided, thus, all elevation values are not available and<br />
shown as zero. These GCPs coordinates included with the ASTER scene are calculated<br />
from the sensor and ground processing and are used to transfer these values to the<br />
ground. They are only as accurate as the satellite ephemeris information. To view the<br />
existing GCPs, choose the import GCPs from file icon (figure 3.21), then select image 3N<br />
(similar GCPs number in image 3B) to load the available GCPs on the image (figure<br />
3.22). The 121 GCPs are evenly distributed in a grid form over the entire image of each<br />
ASTER scene as shown in figures 3.23 to 3.25.<br />
Figure 3.21: Importing GCPs from file using the 8 th icon on the toolbar.<br />
Figure 3.22: loading the 121 already available GCPs from image 3N file.<br />
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Figure 3.23: Dead Sea band 3N GCPs.<br />
Figure 3.24: Dead Sea band 3B GCPs.<br />
Figure 3.25: The image layout of bands 3N and 3B showing the location of all 121 GCPs<br />
in the Dead Sea ASTER image.<br />
The following step in the process is collecting tie points which aims to adjust and<br />
correlate the two stereo images together. Using tie points allows automatic extraction of<br />
the DEM from the generated 3N and 3B images only (figure 3.262). However, the<br />
addition of GCPs to these images will permit precision geocoding and scaling of DEMs<br />
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in the z direction (Selby 2003). Tie points are basically features that are clearly<br />
recognizable in two or more images and can be used as reference points to identify how<br />
images relate to each other (Geomatica 2003), as illustrated in figure 3.27.<br />
Figure 3.26: Start the Collect Ground Control Points (GCPs) and Tie Points (TPs)<br />
manually function from bands 3N and 3B by using the 2 nd icon on the OrthoEngine<br />
toolbar.<br />
Figure 3.27: An image shows how two images connect through a tie point (From<br />
Geomatica 2003, figure 5.2, p. 51).<br />
Selecting a set of quality tie points (minimum of six) which are spread over the<br />
images is vital to the accuracy of the final DEMs. Therefore, tie points should be features<br />
that can be accurately identified at the resolution of the raw image. It is important to<br />
choose tie points that are close to the ground and away from features that rise above the<br />
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ground such as buildings and mountains because high features may appear to lean in one<br />
image but may not in the other. In addition, shadows are not suitable to be used as tie<br />
points since they are not a permanent feature and may move from one image to another.<br />
Streets and highways intersection are the best features to be selected as tie pints since<br />
they are permanent feature and easy to identify in the images (Geomatica 2003).<br />
To start collecting tie points manually (figure 3.28), both images should be active<br />
during this process where the one from which points are being collected would be labeled<br />
Working while the other is labeled Reference (figure 3.29). After choosing a single tie<br />
point from the working image, it is easy to collect the same point in the other image by<br />
switching to the reference image and select the same point. All tie pints are recorded in<br />
the tie point collection window (figure 3.30 and table 3.3). It is highly recommended to<br />
zoom in to see the detail in the image and use both Auto Locate and Bundle Update<br />
features during tie point collection. The auto locate feature is employed by OrthoEngine<br />
to estimate the position of the points by using an automatic correlation method once it has<br />
adequate information to calculate the math model. Usually, this function works best when<br />
there are three tie points existing per image. On the other hand, the bundle update feature<br />
allows OrthoEngine to perform the bundle adjustment every time a tie point is added to<br />
the project. This can assist to determine the dependability of the point being selected for<br />
the project (Geomatica 2003).<br />
Figure 3.28: Collecting tie points manually from both images by choosing the 9 th icon on<br />
the OrthoEngine toolbar.<br />
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Figure 3.29: Opening both uncorrected 3N and 3B images to manually collect tie points.<br />
Figure 3.30: Collecting tie point window for Aqaba image 3N including the type of tie<br />
point, their residual errors, their x, y coordinates, and z values on each image.<br />
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DEM Coverage Area Dead Sea North Araba South Araba Aqaba<br />
Number of tie points 24 23 17 20<br />
Manual tie points (T) 20 18 11 15<br />
Automated tie points (AT) 4 5 6 5<br />
Table 3.3: Number and type of tie points in each DEM coverage area.<br />
When done collecting tie points manually, running the Automatically Collect Tie<br />
Points from the 10 th icon on the GCP/TP Collection list of the OrthoEngine (figure 3.31)<br />
using the default inputs increase the chances of finding more tie points to enhance the<br />
overall DEM resolution. Since tie points are simply matching points in two images,<br />
collecting points can be automated in OrthoEngine utilizing image correlation techniques.<br />
On the automatic tie point collection window, setting the tie point distribution pattern will<br />
enable better automatic tie point matching. The number of tie points per area was set to<br />
nine points to be distributed uniformly over the entire image. While the matching<br />
threshold that indicates the minimum correlation score that will reflect a successful<br />
match, which is represented by any value ranging from zero indicating no correlation to<br />
one signifying the best correlation has been set to 0.75 (Geomatica 2003, Selby 2003), as<br />
demonstrated in figure 3.32. Further extensive information regarding image correlation<br />
principles and image matching techniques can be found for instance in (Ebner and<br />
Heipke 1988, Förstner 1992, Hannah 1988, Heipke 1996, 1992, 1989, Mahn 1989).<br />
Figure 3.31: Automatically Collect tie points.<br />
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Figure 3.32: Automatically Collect tie points uniformly over an entire image.<br />
On the tie point collection window (figure 3.30), the residual error indicates the<br />
residual difference in pixels between the coordinates that were entered for the tie points, a<br />
typographical mistake, or an error in the position of the tie points on the raw image.<br />
Typically, for every tie-point a 3D point on the ground is computed. This 3D ground<br />
point is reprojected through the rigorous ASTER math model to a new image coordinate.<br />
All the tie points are used to estimate the exterior orientation of the stereopair and so the<br />
reprojected 3D point will not fall exactly where you measured it. Residual errors do not<br />
necessarily reflect errors in the tie points, but rather the overall quality of the math model.<br />
Such errors might denote bad points, but usually they indicate the quality of the<br />
computed math model to fit the ground control system. In general, high residual errors<br />
suggest a poor model solution which is a result of inaccurate tie points, errors of the<br />
projection or datum, inadequate tie points, or unsatisfactory distribution of the tie points<br />
over the image (Geomatica 2003).<br />
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Figures 3.33 and 3.34 show tie points in both 3N and 3B image of the North<br />
Araba area. The T indicates manual tie point while TA indicates an automated tie pint<br />
collection. Finally, to view the distribution of the collected tie pints within the 3N and 3B<br />
images, choose the display overall image layout from the 11 th icon on the OrthoEngine<br />
GCP/TP Collection list toolbar as in figures 3.35 and 3.36.<br />
Figure 3.33: Band 3N tie points (North Araba). Figure 3.34: Band 3B tie points (North<br />
Araba)<br />
Figure 3.35: Displaying overall image layout from both images.<br />
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Figure 3.36: Image layout of both bands 3N and 3B for the North Araba scene.<br />
-Step Three: Math model calculations<br />
Once all of tie points have been collected from stereo images, then a bundle<br />
adjustment ought to be performed to compute the photogrammetric model using the<br />
orbital and ASTER sensor ephemeris information in addition to tie points and GCPs if<br />
available (Geomatica 2003, Selby 2003). The bundle adjustment uses the tie points and<br />
the knowledge of the sensor geometry and orientation to calculate the best fit for all<br />
images used in the project to generate the DEM simultaneously (Geomatica 2003), as<br />
shown in figure 3.37.<br />
Figure 3.37: Running Model Calculation to perform bundle adjustment.<br />
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-Step Four: Creating epipolar images<br />
As mentioned earlier, OrthoEngine uses image correlation to extract matching<br />
pixels in the two stereo images and they apply the season geometry computed from the<br />
math model to calculate the x, y, and z positions, as shown in figure 3.38. Epipolar<br />
images are stereo pairs that are reprojected in order that the left and the right images have<br />
an ordinary orientation, and matching features within the images appear a long a common<br />
x axis. The main purpose of creating epipolar images is to eliminate any offset between<br />
them in the y axis direction. Besides, epipolar images accelerate the autocorrelation pixel<br />
matching algorithm and process that creates DEMs exploiting the stereo overlap area<br />
between the epipolar images and diminish the possibility of incorrect matches due to the<br />
fewer pixels it searches to find a match (Geomatica 2003, Selby 2003).<br />
Figure 3.38: Creating a DEM from stereo pairs using image correlation (From Geomatica<br />
2003, figure 6.1, p. 69).<br />
To create epipolar images start with initiating the Create epipolar image window,<br />
which is the 1 st icon located under the DEM from Stereo list on OrthoEngine toolbar<br />
(figure 3.39). Using the User Select option will allow the manual selection of the stereo<br />
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pairs for each DEM to be extracted. In the left and right image window, normally band<br />
3N is assigned as the left image while band 3B to the right. After that, add the 3N and 3B<br />
stereo images to the Epipolar Pairs Table using all channels. Then select epipolar images<br />
from the List of Epipolar Pairs and set the working cache to at least 256MB, then click<br />
save setup to store all entered options. Finally, click on the Generate Pairs button to start<br />
the epipolar images generating process (Geomatica 2003) (figure 3.40).<br />
Figure 3.39: Create Epipolar image icon.<br />
Figure 3.40: Generate Epipolar images window.<br />
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-Step Five: Extracting DEMs<br />
Automatic DEM extraction is the final step in the DEM generating process.<br />
Starting the function using the 2 nd icon on the OrthoEngine toolbar under DEM from<br />
Stereo list (figure 3.41) will launch the Automatic DEM extraction window (figure 3.42).<br />
To finalize the extraction process, the output DEM file requires a name and a path to be<br />
saved to. Afterward, choose all images in the DEM Bounds to use the extents of all the<br />
images in the Stereo Pair Selection table as the extents of the DEM then click the<br />
Recompute icon to adjust the image size, the DEM resolution (30m), and recalculate<br />
extents, then finally click Start DEM Extraction to generate the geocoded DEM file<br />
(Geomatica 2003). Table 3.4 summarizes the options used in DEM automatic extraction<br />
of all epipolar images for the study area. All elevations were based on the topographic<br />
maps of southern Jordan available at scales of 1:50,000, 1:100,000, and 1:250,000.<br />
Figure 3.41: Extract DEM Automatically icon.<br />
DEM Coverage Area Dead Sea North Araba South Araba Aqaba<br />
Minimum Elevation -650m -600m 0m 0m<br />
Maximum Elevation 1800m 1950m 1800m 1800m<br />
Failure Value -600 -9998 -100 -100<br />
Background Value -9999 -9999 -150 -150<br />
DEM Detail Medium Medium Medium Medium<br />
Output DEM Channel Type 16-bit Signed 16-bit Signed 16-bit Signed 16-bit Signed<br />
Pixel Spacing Interval<br />
(DEM resolution)<br />
2 (30m) 2 (30m) 2 (30m) 2 (30m)<br />
Fill Holes and Filter Yes Yes Yes Yes<br />
Create Score Channel Yes Yes Yes Yes<br />
Create Geocoded DEM Yes Yes Yes Yes<br />
Table 3.4: Options used for all DEMs extraction processes within the study area.<br />
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Figure 3.42: Automatic DEM extraction window showing all used options for Aqaba<br />
DEM.<br />
Failures in the DEM extraction occur in areas with very low contrast such as<br />
shadows, clouds, snow, and water bodies. Usually, small failure holes in the DEM are<br />
filled automatically by interpolation, while large failure areas necessitate manual editing<br />
using filters to complete the DEM (Selby 2003). Specifying failure values is very useful<br />
when interpolating these pixels in subsequent DEM editing. The Background value<br />
categorizes the pixels with no data that lies outside the extracted DEM overlap area so<br />
they could be distinguished from elevation values. Alternatively, the maximum and<br />
minimum elevations are employed to estimate the search area for the correlation, which<br />
increase the speed of the correlation process and reduce error (Geomatica 2003).<br />
Therefore, due to the high contrast between the mountains and valleys elevations in the<br />
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North Araba and the Dead Sea images, the minimum and maximum elevation values in<br />
these areas have been expanded by ±150m to enable enhanced DEM results.<br />
The Fill Holes and Filter option is used to enhance the quality of the DEM<br />
product by automatically filtering the elevation values and interpolating the failed areas.<br />
Also, turning on the Create Score Channel option generates an extra image channel that<br />
classifies the failed pixels during correlation to the ground for each DEM pixel, which<br />
assist evaluating the success of the procedure. Finally, choose the Create Geocoded DEM<br />
to merge and geocode the epipolar DEMs (Geomatica 2003).<br />
During DEM extraction, image correlation is used to locate similar features on<br />
both the left and right stereo images. Matching these features is normally achieved by a<br />
hierarchical approach utilizing a pyramid of reduced resolution images. This method<br />
creates a multi-resolution image pyramid that consists of a base image and a series of<br />
sequentially smaller sub-images, each at half the resolution of the previous image (figure<br />
3.43). This correlation technique expedites the image correlation operation and<br />
diminishes the mismatches measures. The first correlation attempt is executed on very<br />
coarse versions of the images. This facilitates OrthoEngine matching major features by<br />
precisely constructing the foundation for advanced correlation attempts. The next<br />
attempts are carried out on higher resolution images until finally the correlation is<br />
performed on images at full resolution to provide the highest accuracy of the terrain in<br />
the DEM (Geomatica 2003, Ismert et al. 2003).<br />
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Figure 3.43: The multi-resolution image pyramids method of creating reduced resolution<br />
images to optimize display performance (Modified from Ismert et al. 2003, figure 5, p.<br />
6).<br />
3.6.1.4. DEMs editing process<br />
During the DEM extraction process few missing data and little failure holes with<br />
unsatisfactory resolution were produced in dispersed locations. Most failure holes are a<br />
few meters wide, the largest is about 4.5km across located in South Araba area. The<br />
interpolation of ASTER data normally solves such problems by restoring the failure holes<br />
of 1km or lees with elevation values. In this case, since there are several failure holes of<br />
dissimilar sizes that were scattered randomly in the highest and lowest elevation areas<br />
within the JDTZ, the procedure of editing DEM were applied to substitute for these<br />
missing data.<br />
These missing data occurred when using the full resolution DEM (pixel sampling<br />
of 1, yielding 15m DEM) due to the high contrast in elevation of the terrain relief<br />
between mountains and valleys. Nevertheless, the major mountains and valleys in the<br />
study area are identifiable and well defined to proceed with digital geomorphic analysis.<br />
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Thus, medium DEM detailed resolution (pixel sampling of 2, yielding 30m DEM) was<br />
generated, which is suggested for most satellite images to accelerate the process and<br />
produce smooth DEMs (Geomatica 2003). Due to the geographic nature of the JDTZ, it<br />
was difficult to recognize and allocate mutual features in both epipolar images during the<br />
process of generating DEM. Therefore, employing the full resolution 15x15m pixel<br />
sampling window increased the probability of image-to-image correlation failure creating<br />
many and larger failure holes that were fewer when using the medium 30x30m pixel<br />
sampling window. Since ASTER is an optical sensor, it is impossible to generate DEMs<br />
in cloud-covered areas or water areas (Tokunaga 1996); as a result, both the Dead Sea<br />
and the Mediterranean Sea show no elevation data. The generated geocoded 30m<br />
resolution DEMs for each ASTER scene are presented in figures 3.44 to 3.47, where the<br />
missing data can be noticed as black holes (i.e. no data) within the DEMs.<br />
Figure 3.44: The Dead Sea generated DEM. Figure 3.45: North Araba generated DEM.<br />
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Figure 3.46: South Araba generated DEM.<br />
Figure 3.47: Aqaba generated DEM.<br />
Following the generation of the DEM, editing can be performed, if required, to<br />
correct out and fill in the failures and missing data. Consequently, the final DEMs and<br />
orthorectified images are valuable for interpretation and analyses of landforms and<br />
geology (Selby 2003). The DEM editing process necessitates another DEM data source in<br />
order to retrieve the missing data. Usually GTOPO30 coarse DEM data is used due to its<br />
global coverage (Fujisada et al. 2001). The DEMs editing method using both Geomatica<br />
Focus and XPace Tools are explained below in details.<br />
-Step One: Importing and subsetting the global DEM<br />
In order to fix the missing data in the generated DEMs of the study area, coarse<br />
DEM data of known elevation values is being used. The global DEM GTOPO30 image<br />
of the Middle East with a horizontal grid spacing of approximately 1km (Campbell 2002)<br />
and has a file extension of HDR is accessible from the USGS website available at<br />
(http://edcdaac.usgs.gov/gtopo30/dem_img.asp), as shown in figure 3.48.<br />
1. Importing the GTOPO30 DEM to PCI Geomatica 9.1 and convert the image<br />
to *.PIX with a new file name and path [File> Utility> Import to PCIDSK><br />
GTOPO30.HDR> file name].<br />
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2. Subsetting the whole Middle East GTOPO30 DEM to fit the JDTZ study area.<br />
Using Tools in Focus window [Tools> Clipping/Subsetting> Enter file name><br />
Set dimensions to subset].<br />
-Step Two: Reprojecting the global DEM<br />
The GTOPO30 DEM data is projected as latitude/longitude, thus, to best fit the<br />
study area the DEM needs reprojection to the UTM zone-36: 30E to 36E, Row: R-24N to<br />
32N, and WGS-84 (E012) ellipsoid.<br />
1. To do so, in Focus [Tools> Reprojection> Enter the GTOPO30 file name> Set<br />
the projection parameters> Resampling = Nearest> Transform Order = Exact><br />
Sampling interval = 1> Source layer = All> Reproject].<br />
-Step Three: Adding New Channels<br />
1. All DEM scenes should be viewed as Pseudocolored images to facilitate<br />
editing, this is done in Focus window as follow: [Layer> Add><br />
Pseudocolored> File name].<br />
2. Adding new channels to each study area scene should be done before starting<br />
fixing any of the DEMs.<br />
3. One bitmap channel that is specified using the special symbol (%%) and two<br />
raster 16-bit signed channels, which is specified using the special symbol (%)<br />
should be added for each DEM file (signed channel allow reading data as<br />
integers of ± values).<br />
4. On the maps tree menu, click on file to add extra channels to the exiting DEM<br />
files [Right click on the file name> New> Raster Layer x2] then repeated the<br />
same step for the Bitmap Layer.<br />
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Figure 3.48: General view of the clipped GTOPO30 DEM of the Middle East showing<br />
the JDTZ study site (Map not to scale).<br />
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-Step Four: Filling the missing values in the study area DEMs<br />
1. This step aims to fill in the missing values of each DEM of the study area by<br />
known values obtained from the GTOPO30 DEM.<br />
2. Using XPace Tool from the Geomatica toolbar (figure 3.49).<br />
3. Each DEM file of the study area is separately combined with GTOPO30 DEM<br />
by performing image mosaicking using the Geometric Correction package and<br />
Image Mosaicking task as follow: [XPace> Geometric Correction> Image<br />
Mosaicking]. Normally, a mosaic composite image is made of joining together<br />
individual images covering adjacent regions on the ground (Campbell 2002,<br />
Sabins 1997). Thus, mosaicking process is basically piecing together several<br />
contiguous, overlapping, or bordering images to ultimately create a uniform<br />
image (Geomatica 2003).<br />
4. Filling the parameters window as indicated below then RUN the application.<br />
FILI: (GTOPO30 DEM file name)<br />
OBIC: 1<br />
FILO: (study area DEM file name)<br />
OBOC: 2<br />
Where FILI indicates the name of the PCIDSK file (i.e. DEM) from which the<br />
input image data is to be read. FILI cannot be the same as FILO, because the bounds of<br />
the two images stored in their georeferencing segment are needed to determine their<br />
overlap, OBIC is the input channel(s) with integer numbers to read from input files on<br />
FILI and stored to output file on FILO, and OBOC is the output channel(s) on FILO to<br />
write the image data to (Geomatica 2003).<br />
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5. Remove all files from the maps tree menu and then reload again as<br />
pseudocolored layers [for each DEM in the study area load only channel 2<br />
(%2)].<br />
6. Repeat procedure 3 to 5 for each of t he four DEMs.<br />
Figure 3.49: The XPace Tool, the 10 th icon on Geomatica Toolbar.<br />
-Step Five: Creating a mask for the missing values<br />
A mask categorizes specific pixels over areas that need editing. Normally, the<br />
mask doesn’t change the values in the areas that it covers, although it assists in<br />
identifying these areas to be replaced with true (or known) elevations from other sources<br />
(Geomatica 2003).<br />
1. Using the EASI modeling to create a mask to the already created bitmap<br />
channel (%%2). In Focus window [Tools> EASI Modeling> Enter file name<br />
of the study area DEM].<br />
2. Run the EASI modeling using the following syntax:<br />
if % 1 = (enter the failed value of each study area DEM e.g. -9998) then<br />
%% 2 = 1<br />
else<br />
%% 2 = 0<br />
endif<br />
-Step Six: Filling the missing values within the mask<br />
1. Using the EASI modeling to create a mask to the already created bitmap<br />
channel (%%2) and the new raster channel (%2). In Focus window, [Tools><br />
EASI Modeling> Enter file name of the study area DEM].<br />
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2. Run the EASI modeling using the following syntax:<br />
if %% 2 = 1 then<br />
% 1 = % 2<br />
else<br />
% 1 = % 1<br />
endif<br />
3. Remove all images from the maps tree menu and reload the first channel (%1)<br />
of the study area DEM.<br />
-Step Seven: Smoothing the mask and finishing up the whole DEM scene<br />
Filtering of missing data within DEMs will eventually alter the original elevation<br />
values. Thus, filtered portions of the DEMs are used for as a cosmetic procedure for<br />
display purposes and not as an elevation source for the morphometric analysis.<br />
Smoothing the mask was done by utilizing convolution filters which involve the<br />
movement of filter window throughout an image pixel-by-pixel and line-by-line until<br />
covering the whole image. Low pass filter enhances remotely sensed images by blocking<br />
the high spatial frequency details utilizing different size mask of a particular brightness<br />
value and outputs a new images with new brightness values. The size of the mask varies<br />
but usually 3 x 3, 5 x 5, 7 x 7, or 9 x 9 window. A low pass images for each DEM were<br />
produced using a 9 x 9 averaging function mask. Ultimately, the central pixel value<br />
within the mask is replaced by an average of the surrounding nine pixels in the<br />
convolution filter (Campbell 2002, Jensen 1996, 2004, Mather 1999, Moore and Waltz<br />
1993, Sabins 1997).<br />
1. This process is achieved using XPace Tool.<br />
2. Using Average Filter to smooth the mask of the added pixel values for<br />
GTOPO30 DEM due to their coarser resolution compared to the ASTER<br />
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DEM resolution using Image Processing package and Average Filter (FAV)<br />
task [XPace> Image Processing> FAV].<br />
3. Run the application after entering the following data in the parameters<br />
window:<br />
FILE: (file name of the study area DEM)<br />
DBIC: 1<br />
DBOC: 1<br />
FLSZ: 9, 9<br />
MASK: 2<br />
Where FILE is the input DEM file of, DBIC specifies the input channel to be<br />
filtered, DBOC specifies the output channel for the filtered result, FLSZ is the filter size<br />
in units of pixels and lines, in this case a filter size of 9 x 9 pixels/lines window is used,<br />
and MASK indicates the area in the input channel which should be processed, in this case<br />
use the bitmap channel (%%2) to only process pixels under it (Geomatica 2003).<br />
-Step Eight: Loading final DEM<br />
Remove all images from the maps tree menu then reload the raster channel (%1)<br />
of each DEM in the study area. At this point, the DEMs should be completely fixed and<br />
ready to be transferred as an ASCII file to be readable in ArcScene program within the<br />
ArcGIS software for further analyses. The difference between the generated ASTER<br />
30m-pixel resolution DEM(s) and the coarser pixels of the 1Km resolution mask derived<br />
from GTOPO30 DEM could be notices as shown in figures 3.50 to 3.53. Four transfers<br />
are needed for each repaired DEM where only channel (%1) of each fixed DEM being<br />
transferred. This procedure is carried out in Focus window as follow: [File> Utility><br />
Translate> Browse: DEM File name> Destination> Type new DEM ASCII File Name><br />
GRD: Arc/Info Grid (ASCII) as the new file extension].<br />
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Figure 3.50: The Dead Sea final DEM.<br />
Figure 3.51: North Araba final DEM.<br />
Figure 3.52: South Araba final DEM.<br />
Figure 3.53: Aqaba final DEM.<br />
3.6.1.5. Transferring ASTER DEM to GIS environment<br />
GIS has the capability to integrate multiple map layers including DEMs and<br />
satellite imagery and run several analyses to the spatial relationship within these maps<br />
quickly and with no effort (Horsby and Harris 1992). In addition to that, viewing data in<br />
three dimensions in GIS environment give new perspective about the derived DEM data,<br />
adding insights that wouldn’t be readily visible from a planimetric view (Poli et al. 2005).<br />
The three dimensional vector and raster data and DEMs generated in ArcGIS depicting<br />
DEMs and digitized valleys and mountain fronts were imported to ArcScene for further<br />
127
analysis and visualization. Particularly, ArcScene application available with ArcGIS<br />
(ESRI) 3D Analyst extension, allows creating three dimensional maps for visualization<br />
and rendering with a static level of detail control for large datasets (Chrysoulakis et al.<br />
2004, Poli et al. 2005). The incorporation of elevation and terrain data, generally,<br />
improves the management and visualization of geographic data and can enhance<br />
information extraction (Poli et al. 2005). Thus, the developed three dimensional DEM<br />
views using ArcScene will represent the high quality of the generated DEMs and their<br />
potential for more thorough image interpretation (Kamp et al. 2003).<br />
Converting the DEM ASCII files to raster files in the form of ESRI GRID format<br />
to be readable by ArcGIS software and its extensions is achieved using a specific<br />
command line for this purpose. The Command Line window is located under the Window<br />
tab in the ArcMap main menu (within the ArcGIS 9 software). The command line is<br />
simply identifies the current ASCII file format location and convert it into a grid file<br />
format to the same or another path creating a floating-point raster dataset. Floating-point<br />
number (or real number) is a sort of numeric field used for measuring and for storing real<br />
number that can contain a fractional part and a decimal point (e.g. 34.824, 0.0004, and -<br />
9873.21). The decimal point can be in any position in that field, thus, there is no fixed<br />
number of digits before and after the decimal point, that is, the decimal point can float<br />
from one place to another for different valued stored in the filed (Mather 1999). To<br />
perform conversion, insert the following case sensitive command line<br />
ASCIIToRaster_Conversion <br />
FLOAT. An example of the Dead Sea DEM<br />
conversion using this command line would be ASCIIToRaster_Conversion<br />
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C:\All_DEMs\aster_dem_D-S.ascC:\All_DEMs\aster_dem_D-S_newFLOAT. After this<br />
conversion, the DEM data can be imported to GIS environment for any further analysis,<br />
as illustrated in figures 3.54 and 3.55.<br />
Figure 3.54: Portion of the North Araba converted GRID file format (*.GRD) to ASCII<br />
format, notice the failure value (-9999) on the top and the elevation values on the rest of<br />
the file.<br />
Figure 3.55: The converted North Araba DEM using ArcGIS ASCII to Raster command<br />
line.<br />
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3.7. Obtaining Landsat 7 ETM+ imagery<br />
The Landsat imagery could be obtained and downloaded free of charge from the<br />
University of Maryland Institute for Advanced Computer Studies website provided by the<br />
Global Land Cover Facility, Earth Science Data Interface available at<br />
(http://glcf.umiacs.umd.edu/index.shtml). When clicking the “Download Data” button<br />
located on the upper-right part of the screen, a new webpage that has all the available<br />
satellite sensors scenes will appear. For the purpose of this research, Landsat 7 ETM+<br />
sensor was chosen to download the imagery of the JDTZ study area in Jordan that is<br />
available at (http://glcfapp.umiacs.umd.edu:8080/esdi/index.jsp).<br />
Two Landsat scenes were downloaded that cover the study area located within the<br />
JDTZ. Each image carries a unique identification number and the size of the image as<br />
follow: The Dead Sea ETM+ image data is (p174r038_7x20020308.ETM-EarthSat-<br />
Orthorectified) and the Wadi Araba ETM+ image data is (p174r039_7x20020308.ETM-<br />
EarthSat-Orthorectified). The data acquisition date of both scenes is March 8, 2002 and<br />
the data processing date is February 12, 2004. All Landsat data are in the form of<br />
compressed files (*.gz file extension) that are downloadable from the FTP files site<br />
available at (http://glcfapp.umiacs.umd.edu:8080/esdi/ftp?id=37264) where each Landsat<br />
band could be individually downloaded from the FTP link denoted for each band. The<br />
final Landsat imagery is a georectified TIFF images that are projected to the WGS-84<br />
datum and ellipsoid and are compatible with all ESRI GIS products.<br />
3.7.1. Creating ASTER and Landsat composite images<br />
To view and analyze both ASTER and Landsat images in a GIS environment, the<br />
images would be more informative and useful if they are in the form of a color composite<br />
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image. The best combination of three bands of Landsat satellite imagery forming a false<br />
color image of an arid to semiarid region would be 7, 4, and 2 as Red, Green, and Blue,<br />
respectively (Arlegui and Soriano 1998). Toward the differentiation between the Landsat<br />
and ASTER color composite images, the former sensor images were displayed as 7-4-2<br />
composites while the latter as 3-2-1 true color composite images. Having two different<br />
color combination of satellite images will allow flipping back and forth between the<br />
images, which will assist in highlighting mountain fronts and valleys in the digitizing<br />
process and accentuating the differences between the different color image combinations.<br />
The procedures to create color composite images from Landsat and ASTER scenes area<br />
as follow:<br />
-Step One: Import images to the new composite image file<br />
The creation of a composite image depends firstly on the input file initial format.<br />
In case the input image in PIC format there is no need to perform importing, otherwise,<br />
the common Landsat and ASTER images formats such as HDF and/or TIFF need to be<br />
imported to PCIDSK format.<br />
a) Importing the HDF or TIFF files to PIX files first using PCI Focus (File><br />
Utility> Importing to PCIDSK> Source File Name> Destination File Name> Import).<br />
b) In XPace, use the PIX file that you created in the first step as an input to the<br />
composite image that you need to produce. Make sure to import and transfer files in the<br />
order desired to create the composite image (RGB). If an image composite of bands 1, 2,<br />
and 3 needed, then, import band 3 (Red) first, then transfer bands 2 (Green) and 1 (Blue)<br />
respectively. (File> File Utility> Importing to PCIDSK> type the Source File Name><br />
enter the Destination File Name (the name of the RGB composite final image)> Import).<br />
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-Step Two: Transfer imported images<br />
a) In XPace, transfer the other two layers (bands Green and Blue) to the imported<br />
PIX file (the Red band already exists) in step 2. The process is carried out as follow:<br />
(Tools> Transfer Layers> enter the Source File Name (band Red from step 2)> type in<br />
the Destination File Name (band Green)> Select the new image> Add> Select the added<br />
image> Transfer Layers).<br />
b) Repeat the same procedures as in the previous step (2/a) for the last layer (band<br />
Blue).<br />
-Step Three: Create the final composite image<br />
a) In Focus, open the created composite RGB image. Right click on the image><br />
Enhance> Edit LUTs> Click on the Red band histogram once> Save> Save image<br />
w/LTU> Overwrite existing channel> OK). Repeat the same procedures for the other<br />
Green and Blue band histograms.<br />
Lookup tables (or LUTs) consist of an array of the original input pixels and the<br />
corresponding array of enhanced output pixels values that are used to produce the new<br />
composite image. It contains the exact disposition of each combination of red, green, and<br />
blue (RGB) values associated with each 8-bit pixel. Normally, the color of each pixel in<br />
the image is determined by matching it to a set of colors stored in tables that show their<br />
numerical values. Usually there are three LUTs for each of the composite color that is<br />
presented in the form of a graphic display or a histogram (Campbell 2002, Jensen 1996,<br />
2004, 2004, Mather 1999, Sabins 1997). Whereas, histogram is known as a statistical<br />
graph represents the distribution of data points and content of a remotely sensed image as<br />
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a function of some attribute, such as brightness values (Campbell 2002, Jensen 1996,<br />
2004, 2004, Mather 1999, Sabins 1997).<br />
-Step Four: Transfer the final composite image to new format<br />
a) In Focus, transfer the created composite image to TIFF or JPG using (File><br />
Utility> Translate> Source File Name> Destination File Name> Set output format as<br />
TIF/TIFF 6.0> Select all source layers> Add> Select all destination layers> Export). By<br />
the end of this process the final satellite images are ready to be imported to ArcGIS<br />
software and viewed as raster layer with the same projection as of the vector data in the<br />
map project.<br />
3.8. Obtaining vector data<br />
The vector data were obtained from the Digital Chart of the World (DCW). The<br />
scale of the thematic dataset or layers is 1:1,000,000 (or 1cm: 10km), which was<br />
produced in 1993 (Campbell 2002). All layers are compatible with any geographic<br />
information system (GIS) software in the market. The downloaded coverages data are in<br />
interchange file format (*.E00 file extension) originally designed for ArcInfo that is also<br />
readable by ArcView and ArcMap. Interchange files could be converted into coverage<br />
file and in turn into Shapefiles using ArcToolbox, and then by using the projection tool<br />
we can define the coordinate system (e.g. WGS-84) to the Shapefiles. The original DCW<br />
data is projected to geographic longitude/latitude and to decimal degrees and the entire<br />
database is provided by Penn State University Libraries webpage available at<br />
(http://www.maproom.psu.edu/dcw/).<br />
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3.8.1. Converting Interchange files to Shapefiles in ArcToolbox<br />
In order to import the vector data into any GIS environment, the data should be<br />
readable by such software. The downloaded interchange files from the DCW much be<br />
converted into a compatible file format, namely shpafiles, to be loaded into the GIS<br />
software. The steps of converting interchange files to shapefiles are listed below.<br />
-Step One: Importing interchange files (*.00E)<br />
-Under Import to Coverage use the Import from interchange file tool (figure 3.56).<br />
-Browse to input the needed interchange file (in this case road layer was selected)<br />
and assign the output file name and path, then click OK to execute file conversion.<br />
-The result of this conversion is a coverage file of the actual interchange file.<br />
Coverage is a vector-based data storage file that usually represents a single theme and<br />
used to store the location, shape, and attributes of geographic features. It is one of the<br />
main and native vector data formats for ArcGIS that combines spatial data and attribute<br />
data and stores topological relationship among features. Normally, coverage file saves<br />
spatial data in binary files and attribute and topological data is kept in tables. The related<br />
feature attribute tables normally describe and store attributes of the geographic features<br />
(Zeiler 1999).<br />
Figure 3.56: Import from Interchange file window in ArcToolbox.<br />
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-Step Two: Convert Coverage to Shapefile (*.shp)<br />
-Under Export from Coverage use the Coverage to Shapefile tool (figures 3.57<br />
and 3.58).<br />
-Navigate to the roads coverage file created in the previous step to serve as the<br />
input file. Set the feature type to line. Then give the shapefile output file name and path,<br />
and then click OK to perform file conversion using default setting.<br />
-The output file is a shapefile that represents the roads of Jordan.<br />
Figure 3.57: The Coverage to Shapefile tool in ArcToolbox.<br />
Figure 3.58: The Coverage to Shapefile tool window in ArcToolbox.<br />
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-Step Three: Defining Shapefile projection<br />
-Under Projections tool use the Define Projection Wizard (shapefile, geodatabase)<br />
(figure 3.59).<br />
-Browse to the input file (i.e. roads shapefile), highlight the file in the data<br />
window and then click next (figure 3.60).<br />
-Select the coordinate system that suites the study area to be assigned to the input<br />
data then click OK to complete. The coordinate system was set to the spheroid-based<br />
Clarke Geographic Coordinate Systems of 1866 (i.e. spatial reference). This is the default<br />
projection of the downloaded interchange files which is the only projection that is wellsuited<br />
the UTM Projected Coordinate Systems of WGS-84, zone-36 North. The finale<br />
shapefile is ready to be imported into ArcGIS to overlay other layers and images or for<br />
any further analyses.<br />
Figure 3.59: The Define Projection Wizard in ArcToolbox.<br />
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Figure 3.60: The Define Projection Wizard window under Projections in ArcToolbox.<br />
3.8.2. Digitizing vector data<br />
Obviously, as a result of the scale difference between the vector data obtained<br />
form the DCW (scale 1:1,000,000) and the satellite imagery (scale 1:50,000), some<br />
editing to the vector data was necessary to match significant features on the satellite<br />
imagery. Toward this, the shapefiles of Jordan western borders and the Dead Sea<br />
shorelines boundaries (figure 3.61) were modified, as close as possible, to fit the similar<br />
features on ASTER imagery using the Editor tool that exists in ArcMap software.<br />
On the other hand, the capitals and major cities in all of the produced maps were<br />
manually digitized as points. Capital and major cities of the surrounding countries to<br />
Jordan were digitized utilizing the seismic map of the Middle East (Chapter 1, figure<br />
1.22), while the major Jordanian cities were manually digitized using the geologic maps<br />
of Jordan. The digitized points were first created in ArcCatalog as point shapefile and<br />
then projected to the UTM zone-36N and to the WGS-84 ellipsoid. Using the Editor tool<br />
available within the ArcMap software, the capitals and cities were digitized over each<br />
point on the designated map that indicate each location.<br />
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Figure 3.61: Map shows the Dead Sea shoreline (left) and Jordan borders (right) before<br />
(red line) and after (gray line) editing.<br />
3.8.3. Digitizing mountain fronts and measuring sinuosity<br />
Due to the relatively large imagery sizes and the presence of various mountain<br />
fronts and valleys within the study area dictate large processing time, digitizing, and<br />
computations will be performed on a scene-by-scene basis (Lang and Welch 1999). To<br />
increase the possibility of recognizing mountain fronts and valley profiles within the<br />
study area, shaded relieves (Hillshades) of each of the ASTER DEM scenes were created.<br />
Towards this, exchanging the view back and forth between the DEMs and shaded relieves<br />
took place during digitizing mountain fronts and valley profiles process. Shaded relieves<br />
were generated using the 3D Analyst tool in ArcMap based on the elevation data<br />
available in each ASTER DEM scene. In 3D Analyst, pick the raster layer needed to be<br />
generated as shaded relief then click on Surface Analysis and choose Hillshade. Browse<br />
to the destination DEM in the Hillshade window and use default values for both azimuth<br />
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and altitude and 30m for the output cell size. Select a destination to save the Output<br />
shaded relief raster then generate by clicking the OK button. Repeat the same process for<br />
all ASTER DEM scenes, as shown in figure 3.62, an example from the Gulf of Aqaba<br />
area.<br />
Figure 3.62: The Gulf of Aqaba generated DEM (left) and shaded relief (right).<br />
Prior to digitization process it is necessary to create two new polylines (i.e. lines)<br />
shapefiles for each ASTER scenes area using ArcCatalog. One of these lines represents<br />
the vector layer of the mountain fronts and the other serves as the straight front lengths of<br />
each mountain front. The digitization of mountain fronts sinuosity and their<br />
correspondent total straight lengths were based entirely on the criterion mentioned in<br />
section (3.2.1). Using the digitization tool, each mountain front was created<br />
independently, in some cases, pixel-b-pixel to get as close as possible to the mountain<br />
front in each scene of the imagery, until finishing all available fronts in each scene.<br />
Figures 3.63 to 3.74 illustrates the ASTER color composites (3-2-1 as RGB), derived<br />
ASTER DEMs, generates shaded relieves, digitized mountain fronts and valley profiles<br />
139
of each individual ASTER scene in the JDTZ. The overall number of mountain fronts in<br />
the study area are listed in table 3.5 and illustrated in figure 3.75.<br />
Geomorphic form Dead Sea North Araba South Araba Aqaba<br />
Fronts 1 1 4 9<br />
Table 3.5: Overall number of digitized fronts in the JDTZ.<br />
Figure 3.63: Dead Sea ASTER color composite 3-2-1.<br />
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Figure 3.64: Dead Sea ASTER-derived DEM.<br />
141
Figure 3.65: Dead Sea shaded relief.<br />
142
Figure 3.66: North Araba ASTER color composite 3-2-1.<br />
143
Figure 3.67: North Araba ASTER-derived DEM.<br />
144
Figure 3.68: North Araba shaded relief.<br />
145
Figure 3.69: South Araba ASTER color composite 3-2-1.<br />
146
Figure 3.70: South Araba ASTER-derived DEM (portion of the North Araba and Aqaba<br />
DEMs are shown to the north and south, respectively, to cover the fronts and valleys<br />
extension).<br />
147
Figure 3.71: North Araba shaded relief (portion of the North Araba and Aqaba shaded<br />
relieves are shown to the north and south, respectively, to cover the fronts and valleys<br />
extension).<br />
148
Figure 3.72: Aqaba ASTER color composite 3-2-1.<br />
149
Figure 3.73: Aqaba ASTER-derived DEM.<br />
150
Figure 3.74: Aqaba shaded relief.<br />
151
Figure 3.75: An overall map of the mountain fronts and valley profiles within the JDTZ.<br />
152
The achieved calculations of both values were computed in meters without human<br />
intervention using XTools Pro. This appropriate tool provides an accurate length and<br />
elevation measurements (in addition to many other features) and delivers the results in<br />
the form of columns added directly to the specific shapefile attribute table. The XTools<br />
Pro is a freeware ArcMap add-on provided by Data East GIS software development that<br />
functions as any other ArcMap extension and is available to download at<br />
(http://www.xtoolspro.com/). To calculate all lengths using this tool, the XTools Pro<br />
main drop-down menu use the Table Operations, then Calculate Area, Perimeter, Length,<br />
Acres and Hectares. After that a new window appears asking to enter the shapefile need<br />
to be calculated and the desired outcome units. This process creates new columns in the<br />
selected shapefile’s attribute table demonstrating the exact calculated lengths of both<br />
sinuosity and straight length for each mountain front. Finally, calculating the S mf values<br />
for all mountains is achieved by feeding all the data into a Microsoft Excel spreadsheet<br />
and program the mountain front sinuosity formula to compute the final values.<br />
3.8.4. Digitizing valley profiles and measuring elevations and valleys’ widths<br />
After valleys were being identified in the study area, the digitizing process or their<br />
profiles took place. Quite similar to mountain fronts digitization procedure, the digitizing<br />
tool was used to create a straight two dimensional line -that will be turned into a three<br />
dimensional profile in subsequent steps- covering the valley and the mountain peaks on<br />
both sides. Based on the criteria of choosing valley profiles mentioned in section (3.2.2),<br />
all valleys were digitized according to their visual identification that was entirely<br />
restricted to the generated DEMs resolution. The number of the digitized valleys and the<br />
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minimum and maximum valley profiles distances upstream from associated mountain<br />
fronts are listed in table 3.6.<br />
Distance Dead Sea North Araba South Araba Aqaba<br />
Valleys # 22 15 25 36<br />
Minimum 150m 220m 215m 45m<br />
Maximum 2500m 2500m 1100m 1100m<br />
Table 3.6: Digitized valley profiles number and their distances upstream from mountain<br />
fronts in the JDTZ.<br />
When creating valley profile shapefiles in ArcCatalog, it is important to check the<br />
Coordinates will contain Z values box to enable the shapefiles to store three dimensional<br />
data. The three dimensional data generally has an extra z-value for each x,y coordinate<br />
that is typically used to store the vertical height of the coordinate. The z-values can be<br />
viewed and modeled using the ArcGIS 3D analyst extension, in addition the converted<br />
valley profile three dimensional shapefiles would be rendered using ArcScene program to<br />
measure the main three elevations of each valley (i.e. E ld , E rd , and E sc ). The digitization of<br />
valley profiles will serve the purpose of calculating the four unknown elevations of E ld ,<br />
E rd , E sc and V fw values in order to calculate the V f values of each individual valley.<br />
Towards this, the valley profiles will be first converted into a two dimensional cross<br />
section profile to calculate the V fw values. Then, all the valley profiles will be converted<br />
into three dimensional profiles and viewed in ArcScene to measure the elevation values<br />
of each valley individually. Since all the valleys in the study area run approximately in<br />
the east-west direction, as a result, the valley profiles are all oriented in the north-south<br />
direction. Therefore, during the calculation of the V f values, the north end of each valley<br />
profile will represent the east elevation of the valley divide (E ld ), while the south end will<br />
represent the right valley elevation divide (E rd ).<br />
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To calculate the V fw values of each individual digitized valley, the “Create Profile<br />
Graph” located in the ArcGIS 3D Analyst extension is being employed to create a profile.<br />
This graph-like profile will have x and y that symbolize terrain distance and elevation,<br />
respectively. Setting the DEM of the related area to the valley profiles being graphed is a<br />
crucial step to acquire the exact ground measurements. Simply, clicking on the Create<br />
Profile Graph button enables drawing a straight line over each already digitized valley<br />
shapefile. After completing drawing all valley profiles in a specific ASTER DEM<br />
imagery, the drawn profiles could be viewed as graphs by double click on each individual<br />
profile. As illustrated in figure 3.76, the valley floor width can be calculated by<br />
subtracting the values of the beginning and ending of the valley floor using the reference<br />
distance on the x-axes.<br />
Figure 3.76: Calculating the V f value for valley profile #11 in the Dead Sea area (green<br />
and red lines manually added for illustration purposes).<br />
155
To collect the right and left divide and floor (i.e. E ld , E rd , and E sc ) elevation values<br />
of each individual digitized valley, the 3D Analyst “Convert Features to 3D” tool being<br />
utilized. This tool and the conversion procedure allow deriving existing features height<br />
from a surface. For the purpose of this research, the study area generated ASTER DEMs<br />
are being used as the surface to obtain elevation data from. The Convert Features to 3D<br />
process allows the manually digitized polyline, which represent each valley profiles, to<br />
mimic the topography of the valley using the elevation data of the DEM to create a 3D<br />
profile of the actual landscape, as illustrated in figure 3.77.<br />
Figure 3.77: The difference between the (a) 2D image (straight-line) and (b) the actual<br />
3D topography (dotted-line) of a given surface (Modified from ArcGIS Desktop Help,<br />
Linear Interpolation).<br />
The process of conversion two dimensional (2D) shapefile to three dimensional (3D)<br />
features in 3D Analyst is as follow:<br />
1. Add the shapefile of each individual valley profile, which is in the form of a<br />
two dimensional feature and the elevation reference surface to an existing map<br />
in ArcGIS.<br />
2. Click 3D Analyst and choose Convert, and then click Features to 3D.<br />
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3. Locate the valley profile shapefiles that need to be converted into 3D in the<br />
Input Features menu.<br />
4. Click the Raster or T<strong>IN</strong> Surface button and set the source to the Valley<br />
profiles related DEM (i.e. raster data) to gather the features heights.<br />
5. Type the name of the output 3D shapefile and allocate a destination.<br />
6. Finally, Click the OK to execute.<br />
Following the conversion all valley profiles in to 3D features in the study area, the<br />
three dimensional shapefiles need to be converted into points. This important additional<br />
step is performed using the XTools Pro in order to assign each point in the 3D shapefile<br />
to its matching elevation value on the ground. The way this method function is by<br />
collecting the elevation value from the center of each pixel in the DEM where the<br />
polyline passed through (figure 3.78). From the XTools Pro main menu, simply choose<br />
“Feature Conversions”, and then Convert Features to Points. This tool is provides ArcGIS<br />
users with capabilities to convert polygons and polylines to point features with<br />
customizable options. The conversion process is explained below and illustrated in<br />
figure 3.79.<br />
Figure 3.78: Collecting elevations from DEM as shapefile passes raster (a) horizontally,<br />
(b) diagonally, and (c) vertically.<br />
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1. In ArcGIS, add all valley profiles of a single ASTER DEM scene at the time<br />
into the map.<br />
2. Select the "Convert Features to Points" item from the XTools Pro Feature<br />
Conversions menu.<br />
3. From the drop-down list select the “Input feature layer” and select the valley<br />
profiles shapefiles (i.e. polylines) for one of the four DEMs in the study area<br />
to be converted to points.<br />
4. Assign a destination and name to the output layer file to be saved in a<br />
shapefile format, then press the OK button.<br />
Figure 3.79: Converting Aqaba 3D feature to points using XTools Pro.<br />
After performing all point conversions, the XTools Pro “Table Operations” is<br />
being used to translate the created data points of each individual three dimensional<br />
shapefiles into readable tables. From the XTools Pro main menu, choose the Table<br />
Operations option, and then click the “ADD X, Y, Z Coordinates”. After that, a new<br />
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window will appear asking to enter one of the already converted 3D-shapefiles into<br />
points to create provide their X, Y, and Z values. The elevation values are created in the<br />
form of additional three data fields automatically added to the correlated shapefile<br />
attribute tables.<br />
The developed 3D valley profiles exhibit the highest quality of the generated<br />
DEMs in identifying the geomorphologic forms and providing extra details of the exact<br />
points of collecting essential elevation data. Hence, they are best viewed using ArcScene<br />
to extract the elevation values of E ld , E rd , and E sc for each valley in the study area (3.80).<br />
After importing all valley profile 3D shpafiles and DEMs of the study area into<br />
ArcScene, collecting the elevation data (i.e. z-values only) of E ld , E rd , and E sc of each<br />
profile is performed using the information button located in the main toolbar, as<br />
illustrated in figure 3.81. After obtaining the elevation data from the entire valley profiles<br />
in all four DEMs within the study area, this information combined with the already<br />
calculated data of the V fw values of all valleys from the previous step are transferred into<br />
Microsoft Excel spreadsheet. Utilizing the function tool in Excel, the V f equation is being<br />
programmed to perform an automated calculation of the V f values for the entire valley<br />
profiles in the study area.<br />
159
Figure 3.80: General view from the Dead Sea area (Looking east, hillshade shows 2xelevation<br />
exaggeration, map not to scale).<br />
160
Figure 3.81: Collecting elevation data from profile #11 in the Dead Sea area (Looking<br />
east, DEM shows 2x-elevation exaggeration, map not to scale).<br />
161
4. Chapter Four: Results and Discussion<br />
4.1. Introduction<br />
The geomorphic analysis of landscape forms exhibits a great potential for<br />
assessing the tectonic activity of the JDTZ. Theoretically, the morphometric analysis of<br />
mountain front sinuosity (S mf ) and valley floor width to valley height ratio (V f ) indicate<br />
the tectonic activity of the mountain front and its adjacent province. Generally, in arid to<br />
semiarid regions, lower values are associated with V-shaped valleys and reflect high<br />
tectonic activity while higher values are linked to U-shaped valleys indicating a moderate<br />
to low tectonic activity (figure 4.1).<br />
Figure 4.1: Valley profile display of a V-shaped valley in South Araba (left) and a U-<br />
shaped valley in the Dead Sea area (right).<br />
In this chapter the results of the geomorphic indices derived from each ASTER<br />
scene in the JDTZ will be individually discussed and the tectonic activity categories of<br />
the study area presented and discussed. The tectonic activity classes of all mountain<br />
fronts and valley profiles were initially designated based on the tectonic activity ranges<br />
established by Bull and McFadden (1977). Such categorization was adopted because it<br />
has proven to be practical in various regions of different geologic settings. Finally, the<br />
accuracy of the ASTER-derived DEM will be tested based on the elevation accuracy of<br />
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the ASTER satellite data provided in the literature in order to examine their reliability<br />
and effect on the final S mf and V f results. Therefore, the results of these indices will be<br />
examined and compared with the valley profile shapes to generate appropriate tectonic<br />
activity classes of the analyzed landforms in the study area.<br />
4.2. The tectonic morphometric analysis<br />
In previous research (chapter two, section 2.3), none of these studies specified a<br />
precise method of differentiating tectonic activity classes. In contrast, the study<br />
conducted by Bull and McFadden (1977) illustrates a significant overlapping in all of the<br />
three tectonic classes. This research aims to generate discrete ranges of the tectonic<br />
activity classes of both S mf and V f results. Furthermore, the three tectonic activity classes<br />
of the valley profiles were determined entirely according to the assigned tectonic activity<br />
class based totally on the S mf values of the mountain front that these valleys are<br />
associated with. Therefore, in this research the definition of each tectonic class will not<br />
only rely on the S mf calculated values of individual mountain fronts but also will be<br />
derived from the individual valley profile V f results.<br />
Table 4.1 lists concise results of both mountain front sinuosity (S mf ) and the<br />
valley floor width/height ratio (V f ) computations. The tectonic activity classes of the V f<br />
index results are assigned based on the V f mean values as presented in previous studies<br />
(Bull and McFadden 1977, Rockwell et al. 1984, Silva et al. 2003, Wells et al. 1988).<br />
Despite the length of the mountain front of the Dead Sea area that is connected to the<br />
North Araba mountain front, it is still fits the criterion of being a continuous mountain<br />
front and will be considered as one entity referred to as the Dead Sea and North Araba<br />
mountain front. In this regard, both mountain fronts were initially measured separately to<br />
163
check their individual S mf and V f values then were measured as a single mountain front in<br />
the subsequent morphometric analysis computations. Detailed results of all S mf and V f<br />
calculations and description of individual valleys shapes are presented in appendix A, and<br />
illustrated in figure 4.2.<br />
Fronts/Valleys Location<br />
Front#<br />
Length<br />
(Km)<br />
S mf<br />
S mf<br />
Class<br />
# of Valley<br />
Profiles<br />
V f<br />
Mean<br />
Dead Sea 1 67.70 1.07 1 22 0.54 1<br />
North Araba 1 64.63 1.21 1 15 0.50 1<br />
Dead Sea & North Araba 1 132.32 1.14 1 37 0.53 1<br />
South Araba<br />
Aqaba<br />
V f<br />
Mean<br />
Class<br />
1 35.94 1.16 1 6 0.56 1<br />
2 3.62 1.21 1 2 0.75 1 - 2<br />
25<br />
3 32.14 1.28 1 15 0.35 1<br />
4 15.26 1.17 1<br />
2 0.47 1<br />
1 10.52 1.12 1 2 0.16 1<br />
2 14.60 1.22 1 3 0.32 1<br />
3 12.03 1.21 1 2 0.43 1<br />
4 19.98 1.71 2 4 0.67 1 - 2<br />
5 8.07 1.17 1 36 1 0.55 1 - 2<br />
6 10.12 1.07 1 2 0.18 1<br />
7 10.62 1.22 1 4 0.14 1<br />
8 21.31 1.25 1 10 0.26 1<br />
9 22.30 1.13 1<br />
8 0.21 1<br />
Table 4.1: Brief results of all mountain fronts sinuosity (S mf ) and valleys floor width to<br />
valleys height ratio (V f ) analyses.<br />
164
Figure 4.2: The tectonic activity classes of the S mf and V f indices results.<br />
165
4.2.1. Mountain front sinuosity results<br />
The mountain front sinuosity analysis shows the lowest results as 1.07 of two<br />
mountain fronts in both the Dead Sea and Aqaba regions and the highest S mf result as<br />
1.71 in the Aqaba region. The results of the S mf analysis of all mountain fronts within the<br />
JDTZ study area indicate that the majority of mountain fronts are highly tectonically<br />
active representing the tectonic activity class 1. On the other hand, only one mountain<br />
front (front 4) in the Aqaba region yield S mf result of 1.71 which symbolizes the moderate<br />
to low tectonic activity class 2. This particular circumstance might have occurred as a<br />
result of the following two principal reasons. (1) The ASTER satellite imagery and the<br />
generated DEM of the Aqaba region did not extend to cover the total length of mountain<br />
front number 4. Therefore, the analysis of the partial length of the mountain front<br />
sinuosity could not provide the actual S mf value precisely. (2) The mountain front has<br />
experienced modification to its shape due to the prolonged erosion caused by the seasonal<br />
flash floods often occurred in this area causing it to be more sinuous (USGS 1998), where<br />
the latter explanation is interpreted to be the main cause.<br />
4.2.2. The ratio of valley floor width to valley height results<br />
The ratio of the valley floor width to valley height analysis reveals the lowest<br />
value as 0.09 in the Aqaba region while the highest V f result as 1.24 in the South Araba<br />
region. Theoretically, the U-shaped valleys indicate relatively low tectonic activity, while<br />
the V-shaped valleys, as a response to uplift, are associated with high tectonic activity<br />
(Bull 1977b, 1978, Bull and McFadden 1977, Burbank and Anderson 2001, Keller and<br />
Pinter 2002). To examine the relationship between the valley profile shapes and tectonic<br />
166
activity, the percentage of the U- and V-shaped valley profiles were calculated and<br />
summarized in table 4.2.<br />
Valley shape/region Northern region Southern region<br />
U-shaped valley 9/37 = 24.4% 26/61 = 42.6%<br />
V-shaped valley 28/37 = 75.6% 35/61 = 57.4%<br />
Table 4.2: The percentage of the U- to V-shaped valley profiles in the JDTZ.<br />
The valley shape percentage calculations were carried out based on dividing the<br />
JDTZ study area into two regions the southern (South Araba and Aqaba) and northern<br />
(Dead Sea and North Araba) regions with a total of 61 and 37 valleys, respectively. The<br />
separation of the study area into two regions had been implemented due to the<br />
continuation and overlapping of a number of fronts into other adjoining areas (e.g. Dead<br />
Sea into North Araba and South Araba into Aqaba). This method of dividing the study<br />
area into two regions based on the spatial distribution of the mountain fronts and their<br />
initial morphometric analysis was adopt by Rockwell et al. (1984) and Wells et al. (1988)<br />
and found to be valuable for the final evaluation of the tectonic activity classes of the<br />
mountain fronts in these regions. Evidently, the V-shaped valleys in both regions are<br />
abundant, however, the U-shaped valleys in the southern region are more frequent<br />
(42.6%) showing a higher percentages (almost twice the value) in comparison to the<br />
northern region (24.4%) signifying a moderate to less tectonic activity in that particular<br />
region.<br />
Practically, it would be quite difficult to distinguish which area is more<br />
tectonically active than the other since the majority of S mf and V f value results represent<br />
the tectonic activity class 1. Nevertheless, according to the morphometric analysis results<br />
the southern region is being slightly less tectonically active than the northern region.<br />
167
Furthermore, the valley profile shapes in the southern region demonstrate a higher<br />
number of U-shaped compared to V-shaped profiles, which may also be partly<br />
attributable to the presence of the largely sandstone and less granite mountains in the<br />
southern area compared to the predominantly limestone in the Dead Sea and northern<br />
Araba areas (Bender 1974a, 1974b, 1975, 1982, Burdon 1959).<br />
Another factor that might have a minimal impact on the alteration of the valley<br />
shapes is the seasonal flash floods in southern Jordan. As a matter of fact, continuing<br />
flash floods in the dry to semi-arid climates, similar to Jordan, drive the primary incisions<br />
incidents that result in extensive erosion in mountain fronts and valleys based on the<br />
difference in their rock resistance (de Jaeger and de Dapper 2002). Practically, in the<br />
absence of tectonic activity, the weathering and erosion processes have a significant<br />
impact on all rocks regardless of their type and resistance. Thus, not only the tectonic<br />
activity of the region has contributed to the alteration of valley shapes which in turn have<br />
a direct effect of the V f values, but the geology of the area has also played an additional<br />
role due to the presence of relatively soft rock type mountains.<br />
4.3. Seismic activity at mountain fronts<br />
Although, the combined data from all tectonic morphometric index analyses<br />
highlight significant variations in relative and numerical values of the JDTZ tectonic<br />
activity; it is very substantial to integrate current field and historical seismological data in<br />
order to examine the position of recorded earthquakes relative to mountain fronts, and<br />
variations in rocks and weathering processes that have their input to the variations of the<br />
overall calculations (Wells et al. 1988).<br />
168
According to Allen (1975), major earthquakes with high magnitudes have<br />
occurred along faults that are correlated to active mountain fronts. The major earthquake<br />
events in the study area have taken place within or in close proximity to the active<br />
seismic zones that are characterized by several active faults. These events were primarily<br />
distributed along and at the intersections of the major active faults in the JDTZ that<br />
comprises the Dead Sea area in the north, the Aqaba area in the south, and Wadi Araba<br />
region. To better illustrate the distribution of earthquake events in the JDTZ, a tectonic<br />
map has been generated utilizing all available historic and recent earthquake events<br />
recorded in Jordan demonstrating the earthquakes network and mountain fronts<br />
relationship, as shown in figure 4.3.<br />
It is obvious that the recorded earthquake events occurred in the northern and<br />
southern regions of the JDTZ are concentrated within the active tectonic zones. In<br />
addition, the tectonic events occurred close to the examined mountain fronts, which are<br />
also adjacent to the active Dead Sea-Jordan River (zone 1) and the northern part of the<br />
Wadi Araba fault lines (zone 3) indicate that this region has experienced larger<br />
magnitude tectonic activity. On the contrary, frequent small magnitude earthquakes<br />
occurred in the southern region nearby the examined mountain fronts in the southern part<br />
of the Wadi Araba fault line (zone 3), whereas the large number of events occurred<br />
further south in the vicinity of the main fault line of the northern Red Sea and the Gulf of<br />
Aqaba (zone 5), as illustrated in figures 4.3 and 4.4.<br />
169
Figure 4.3: Network of earthquakes-mountain fronts’ relationship on the JDTZ showing<br />
earthquake events of M L 4 to 6 and tectonic zones, 19A.D. to August 1983.<br />
170
Figure 4.4: Network of earthquakes-mountain fronts’ relationship on the JDTZ showing<br />
earthquake events of M L 4 to 6 and tectonic zones, September 1983 to 2005.<br />
171
4.4. The accuracy of ASTER DEM data<br />
Elevation is one of the most important datasets in many natural resource and<br />
geomorphological spatial databases that is often used for DEM construction. The<br />
accuracy of these DEMs and their derived products are of critical significance because<br />
errors in the base data will propagate through morphometric and spatial analyses. This is<br />
principally correct where elevation is derived from DEMs and used with other spatial<br />
data. Therefore, errors in elevation will often cause errors in the generated model outputs<br />
(Bolstad and Stowe 1994, Kamp et al. 2003, 2005).<br />
ASTER sensors provide images with a scale of 1:50,000 (Hirano et al. 2003, Lang<br />
and Welch 1999, Lang et al. 1996, Poli et al. 2005, Toutin and Cheng 2001). Moreover,<br />
the along-track stereo data acquisition eliminates the radiometric variations caused by<br />
multi-date stereo data acquisition, which compensate for the weaker stereo geometry and<br />
ultimately improves the image matching performance. It is possible to produce stereo-<br />
DEMs with excellent accuracy when using ground control points (GCPs) measure with<br />
high precision methods. The GCPs are features that could be clearly identified in the<br />
satellite image which have a known ground coordinate. The relationship between the raw<br />
satellite image and GCPs are determined by associating the pixels in the image to the x,<br />
y, and z coordinated system on the ground (figure 4.5). The main source for the<br />
horizontal and vertical values of such check points come from variety of sources such as<br />
GPS, ground surveys, existing topographic maps, and geocoded images (Chrysoulakis et<br />
al. 2004, Cuartero et al. 2004, Fujisada et al. 2001, Poli et al. 2005, Toutin and Cheng<br />
2001). This is widely used in cloud-free images in arid to semi-arid regions where the<br />
elevation accuracy could reach up to 10m (Fujisada et al. 2001, Toutin and Cheng 2001).<br />
172
Figure 4.5: The relationship between the ground and the image coordinate systems<br />
(Geomatica 2003, figure 5.1, p. 33).<br />
Nevertheless, a significant feature of the ASTER stereo system concept is to<br />
generate high quality DEM data without referring to GCPs for individual scenes<br />
depending on the spacecraft ephemeris and the instrument parameters (Fujisada et al.<br />
2001, Kamp et al. 2003, 2005). Therefore, relative DEM is defined as elevation data<br />
generated by not using GCPs, and derived from ASTER stereo pair image using stereo<br />
matching method. On the other hand, absolute DEM requires referencing to a map<br />
coordinate system using GCPs of know locations on the ground to enhance the elevation<br />
data generated from ASTER stereo pair image (Lang and Welch 1999, Tokunaga et al.<br />
1996). Normally, ASTER DEMs with relative accuracy can be used productively to assist<br />
mapping, geomorphic, geologic, tectonic, landform, and a range of environmental studies<br />
in remote areas of rugged terrain (Hirano et al. 2003, Lang and Welch 1999).<br />
ASTER is a relatively recent sensor and there is little research focusing it its DEM<br />
accuracy. In fact, most researches that analyses the accuracy of DEM generated were<br />
173
performed mainly on simulated ASTER data (Abrams and Hook 1995, Lang and Welch<br />
1999, Welch et al. 1998, Cuartero et al. 2004). However, Lang and Welch (1999) suggest<br />
that the root mean square error (RMSE) for elevation values in ASTER DEM should be<br />
in the range of ±10m to ±50m, which is a broad range to define the accuracy of a product,<br />
other researches suggest a DEM elevation accuracy of less than one pixel size (15m) and<br />
up to ±7m (Cuartero et al. 2004, Hirano et al. 2003), where normally the RMSE values<br />
are on the order of ±7m to ±30m (Kamp et al. 2005). Commonly, a DEM created from<br />
ASTER imagery can be expected to have a vertical accuracy of about ±25m. However, in<br />
areas with less vegetation or man-made features, the accuracy can rise to approximately<br />
±10m. Such DEMs are generated with scales of 1:50,000 to 1:100,000 that are useful for<br />
small to medium scale mapping applications and the interpretation of macro- and<br />
mesorelief in areas where high-accuracy commercial DEMs data products are not<br />
available (Kamp et al. 2003, Selby 2003).<br />
ASTER DEMs which were created using GCPs typically produce absolute<br />
elevations (Chrysoulakis et al. 2004) and fully scaled and precision located DEMs and<br />
orthoimages (Selby 2003). In general, the elevation error when using high accuracy GCPs<br />
is less than 15m (Fujisada et al. 2001). Assuming the parallax difference in the range of<br />
0.5 to 1.0 pixels (i.e. 7-15m), the root mean square error (RMSE) of the elevation error is<br />
expected to be in the ±12m to ±26m range. The planimetric and elevation accuracy of the<br />
ASTER produced DEM were found to be ±15m and ±12.4m, respectively, and<br />
considered quite satisfactory for large study areas (Chrysoulakis et al. 2004). According<br />
to previous studies on ASTER derived DEMs, the vertical accuracy is approximately<br />
between ±7 to ±15m and horizontal accuracy of about one pixel with a mean values<br />
174
smaller than one pixel, while the RMSE and standard deviation are slightly larger than<br />
one pixel size (Cuartero et al. 2004, Hirano et al. 2003, Poli et al. 2005).<br />
Based on the study conducted by Hirano et al. (2003), the evaluations of ASTER<br />
DEMs vertical accuracy created by automatic stereo correlation method using PCI<br />
OrthoEngine indicate that an approximate RMSE for z-values of ±7m to ±15m and up to<br />
±10m, where occasionally ±8.6m can be expected when using good quality and adequate<br />
tie pints or GCPs (Hirano et al. 2003).<br />
4.5. ASTER DEM error test<br />
The extraction of topographic information from generated DEMs is becoming a<br />
common method in geomorphic analysis and surface modeling processes. Therefore, it is<br />
essential to generate a DEM with great precision that is able to represent the terrain as<br />
accurately as possible, which eventually will determine the reliability of the<br />
morphometric analysis results (Kamp et al. 2003).<br />
In the case of DEMs, the errors are of attributive type implying an incorrect<br />
assignment of altitude and they modify the z-values. These errors commonly appear in<br />
the creation process of DEMs, both by automatic and manual procedures. The automatic<br />
errors are generated mainly by automatic stereo correlation methods that may have<br />
operative problems as a result of low contrasts in images, ambiguities due to the<br />
repetition of objects of periodic patterns (Felicísimo 1994). Previous researches (Cuartero<br />
et al. 2004, Hirano et al. 2003, Poli et al. 2005) have pointed out that the vertical accuracy<br />
(i.e. elevation) of the ASTER generated DEMs in areas of less vegetation could be on the<br />
order of ±7m to ±30m and can roughly reach ±10m. As an example, if the elevation in a<br />
given location is 1000m in the generated ASTER DEM, this means that the elevation<br />
175
could either be 990m or 1010m. Therefore, the ASTER derived DEMs will definitely<br />
have a direct impact on the overall results of the tectonic geomorphic analysis of the<br />
mountain fronts and valleys used in the research.<br />
In most articles, critical analyses on the error sources using GIS application are<br />
noticeably absent, and that derived products are presented without any estimate of their<br />
accuracy (Felicísimo 1994). Although, testing the accuracy of ASTER elevations is<br />
beyond the scope of this research; using variance-covariance error propagation to<br />
calculate uncertainties (or errors) and the variance values will shed the light on the<br />
accuracy of the calculated tectonic geomorphic indices results in terms of vertical<br />
elevation accuracy and suitability to the actual study area elevation. This means,<br />
evaluating the generated DEMs quality and measuring their reliability in providing the<br />
needed results to serve the purpose of the research.<br />
Error propagation techniques are used to evaluate the resulting errors (e.g.<br />
standard deviation) in quantities that are calculated from a set of measurements (Mikhail<br />
and Gracie 1977, Taylor 1997). This method of computing the magnitudes of errors in<br />
measurements are based upon the assumption that the measurement errors are already<br />
known and given. Practically, if the errors are know they could be simply eliminated by<br />
applying accurate corrections leaving nothing to propagate. Alternatively, if random<br />
errors were considered, even though the specific values of the random errors are not<br />
know, studying the effect of their effect is still possible. In this case, the probability<br />
distributions of the errors are used instead of dealing with the actual error values, or,<br />
equally, working with the probability distributions of the corresponding measurements<br />
and calculated quantities. Therefore, if the set of measurements are represented by the<br />
176
andom factor x, and the calculated quantities are represented by the random vector y<br />
such that y = f ( x)<br />
, then the propagation involves finding the combined probability<br />
distribution of y by specifying the joint probability distribution of x. This can be<br />
accomplished by limiting the consideration to a linear function of x or to linearized forms<br />
of nonlinear functions of x simply by employing the propagation of variances and<br />
covariances (Mikhail and Gracie 1977).<br />
Since variances and covariances are expectations, therefore calculating the<br />
variance-covariance propagation is best accomplished using the approach of defining<br />
variances and covariances in terms of sums calculated from samples of infinite size, in<br />
our case of only four variables (Mikhail and Gracie 1977). Consider a dependent variable<br />
(i.e. random variable) y as a linear combination of an independent variable x that consists<br />
of four variables namely V fw , E ld , E rd , and E sc representing the acquired vertical<br />
(elevations) and horizontal (valley floor width) measurements of the V f index equation<br />
expressed in a linear regression equation such that:<br />
y = Ax + b<br />
In which A is a 4 x 4 coefficient matrix, and the b is the regression coefficient constant<br />
(Mayer 1990, Mikhail and Gracie 1977). Simply, the y value equals the sum of the<br />
constant b that represents the point, at which the line intercepts the y-axis, plus the<br />
product of the slope x times the A value. Similarly, the line’s y intercepts b demonstrates<br />
the y value when A = 0. The line’s slope x shows the amount of change in y units for oneunit<br />
change in A (Knoke et al. 2002, Pipes and Harvill 1970). So, the previous equation is<br />
written more formally given a functional relationship between several measured variables<br />
as:<br />
177
y = Vfwx + Eld x + Erd x + Escx + b<br />
If the deviation of the calculated values of y from its mean value µ y is:<br />
∆ y = y − µ y<br />
It can be show that:<br />
∆ y = V<br />
fw∆ x + Eld ∆ x + Erd∆ x + Esc∆<br />
x<br />
Defining the variances and covariances of y in terms of the existing four random<br />
variables q representing V fw , E ld , E rd , E sc by applying the ith sample component such as:<br />
σ<br />
1<br />
q<br />
2 2<br />
y<br />
= lim ∑ ∆yi<br />
q→∞<br />
q i=<br />
1<br />
The variation in dV f as a function of the uncertainties in V fw , E ld , E rd , and E sc can<br />
be derived by taking the partial derivative of the V f index equation (Pipes and Harvill<br />
1970, Ruffhead 1998, Skoog and Leary 1992, Taylor 1997). Partial derivative of a<br />
function of multiple variables involves the derivative with respect to one of those<br />
variables with the others held constant, that is:<br />
2 Vfw<br />
V<br />
f<br />
=<br />
[(E - E ) + (E - E )]<br />
ld sc rd sc<br />
⎡ 2 ⎤ ⎡ ∂V<br />
fw ⎤ ⎡ ∂V<br />
fw ⎤<br />
dV<br />
f<br />
= ⎢ ⎥ dV<br />
fw<br />
+ ⎢ ⎥ dEld + ⎢ ⎥ dErd<br />
+<br />
⎣(E ld<br />
- E<br />
sc<br />
) + (E<br />
rd<br />
- E<br />
sc<br />
) ⎦ ⎣( ∂Eld<br />
) ⎦ ⎣( ∂Erd<br />
) ⎦<br />
⎡ ∂V<br />
fw ⎤<br />
⎢ ⎥ dE<br />
⎣( ∂Esc<br />
) ⎦<br />
sc<br />
⎡ 2 ⎤ ⎡ −2V<br />
fw ⎤<br />
dV<br />
f<br />
= ⎢ ⎥ dVfw + ⎢ 2 ⎥ dEld<br />
+<br />
⎣(E ld<br />
- E<br />
sc<br />
) + (E<br />
rd<br />
- E<br />
sc<br />
) ⎦ ⎣(E ld<br />
- E<br />
sc) + (E<br />
rd<br />
- E<br />
sc)<br />
⎦<br />
⎡ −2V<br />
fw ⎤ ⎡ 4V<br />
fw ⎤<br />
⎢ 2 ⎥ dEld<br />
+ ⎢ 2 ⎥ dE<br />
⎣(E ld<br />
- E<br />
sc) + (E<br />
rd<br />
- E<br />
sc<br />
) ⎦ ⎣(E ld<br />
- E<br />
sc) + (E<br />
rd<br />
- E<br />
sc)<br />
⎦<br />
sc<br />
178
Consequently, to develop a relationship between the standard deviation and the V f<br />
and the standard deviations of V fw , E ld , E rd , and E sc it is necessary to square the previous<br />
equation (this equation is true if there is no correlation), thus the linear function is<br />
presented as:<br />
σ = a σ + b σ + c σ + d σ<br />
2 2 2 2 2 2 2 2 2<br />
Vf Vf Eldf Erd Esc<br />
Generally, it is more convenient to express the regression equations in matrix<br />
form (Mayer 1990), considering the covariance matrix of the random four variables as:<br />
S<br />
xx<br />
2 2 2 2<br />
⎡σVfw σ<br />
Eld<br />
σ<br />
Erd<br />
σ ⎤<br />
Esc<br />
⎢ 2 2 2 2 ⎥<br />
σ<br />
Eld<br />
σ<br />
Eld<br />
σ<br />
EldErd<br />
σ<br />
EldEsc<br />
= ⎢<br />
⎥<br />
⎢<br />
2 2 2 2<br />
σ<br />
Erd<br />
σ<br />
EldErd<br />
σ<br />
Erd<br />
σ<br />
ErdEsc ⎥<br />
⎢<br />
2 2 2 2<br />
⎥<br />
⎢⎣<br />
σ<br />
Esc<br />
σ<br />
EldEsc<br />
σ<br />
ErdEsc<br />
σ<br />
Esc ⎥⎦<br />
2<br />
The preceding equation can be easily expressed in the matrix form where σ<br />
Vf<br />
is<br />
the variance of V f such that:<br />
σ = AS A'<br />
2<br />
Vf<br />
xx<br />
where A is the coefficient matrix and<br />
A ' is the coefficient matrix transpose (Mayer 1990,<br />
Mikhail and Gracie 1977). Substituting the coefficient matrix A into the foregoing<br />
equation yields (this equation is true if there is correlation):<br />
σ<br />
2<br />
Vf<br />
=<br />
[ a b c d ][ S ]<br />
xx<br />
⎡a⎤<br />
⎢<br />
b<br />
⎥<br />
⎢ ⎥<br />
⎢c<br />
⎥<br />
⎢ ⎥<br />
⎣d<br />
⎦<br />
This result in:<br />
179
σ<br />
2<br />
Vf<br />
=<br />
[ a b c d ]<br />
⎡σ σ σ σ<br />
⎢<br />
⎢σ σ σ σ<br />
⎢σ σ σ σ<br />
⎢<br />
⎢⎣<br />
σ σ σ σ<br />
2 2 2 2<br />
Vfw Eld Erd Esc<br />
2 2 2 2<br />
Eld Eld EldErd EldEsc<br />
2 2 2 2<br />
Erd EldErd Erd ErdEsc<br />
2 2 2 2<br />
Esc EldEsc ErdEsc Esc<br />
⎤ ⎡a⎤<br />
⎥ ⎢<br />
b<br />
⎥<br />
⎥ ⎢ ⎥<br />
⎥ ⎢c<br />
⎥<br />
⎥ ⎢ ⎥<br />
⎥⎦<br />
⎣d<br />
⎦<br />
All elevation values for the independent variables E ld , E rd , and E sc were obtained<br />
using the same DEM to calculate valley profile values (V f ) in each satellite scene of the<br />
JDTZ. Presuming no fluctuation in the acquired elevation values of these independent<br />
variables, logically, any error in the DEM will affect all calculated measurements, and as<br />
a result the correlation value of these variables will be very high. Therefore, when the<br />
components of the random variables are independent, the covariance matrix<br />
Sxx<br />
is<br />
diagonal (Mikhail and Gracie 1977). Ideally, the observed errors are obtained by<br />
collecting control points using GPS and compare it to the generated DEM to create an<br />
absolute DEM. Nevertheless, since the assumed ASTER vertical elevation error is ±10m<br />
(i.e. E ld , E rd , E sc ), and the ASTER generated DEMs horizontal accuracy (i.e. pixel size,<br />
2<br />
V fw ) might shift in the order of half a pixel (30m/2 = 15m), thus, the V f variance σ<br />
Vf<br />
is<br />
2<br />
equal to σ (10m 2 = 100) and<br />
Eld , Erd , Esc<br />
matrix is expressed as follow:<br />
2<br />
σ<br />
Vfw<br />
(15m 2 = 225), respectively, and the covariance<br />
S xx<br />
⎡225 0 0 0 ⎤<br />
⎢<br />
0 100 95 95<br />
⎥<br />
= ⎢<br />
⎥<br />
⎢ 0 95 100 95 ⎥<br />
⎢<br />
⎥<br />
⎣ 0 95 95 100⎦<br />
Assuming the correlation between the independent variables E ld , E rd , and E sc is<br />
0.95 (Cor Eld, Erd, Esc = ρ = 0.95). Therefore, the covariance of the elevation of the<br />
independent variables is expressed as:<br />
180
( σ<br />
ei<br />
)<br />
ej<br />
ρ = where i = 1,2,3 and j = 1,2,3<br />
( σ xσ )<br />
eiej<br />
ei<br />
ej<br />
σ = ρ σ xσ )<br />
(<br />
ei ej<br />
σ<br />
eiej<br />
= 0 .95(10x10)<br />
= 95<br />
Thus, after substituting this value the final integrated equation is expressed as:<br />
σ<br />
2<br />
Vf<br />
=<br />
[ a b c d ]<br />
⎡σ<br />
⎢<br />
⎢<br />
⎢<br />
⎢<br />
⎢⎣<br />
0 0 0<br />
2<br />
Vfw<br />
0<br />
2<br />
σ<br />
Eld<br />
95 95<br />
0 95<br />
2<br />
σ<br />
Erd<br />
95<br />
2<br />
0 95 95 σ<br />
Esc<br />
⎤ ⎡a⎤<br />
⎥ ⎢<br />
b<br />
⎥<br />
⎥ ⎢ ⎥<br />
⎥ ⎢c<br />
⎥<br />
⎥ ⎢ ⎥<br />
⎥⎦<br />
⎣d<br />
⎦<br />
This result in the following equation after substituting the covariance matrix values:<br />
σ<br />
2<br />
Vf<br />
=<br />
[ a b c d ]<br />
⎡225 0 0 0 ⎤ ⎡a⎤<br />
⎢<br />
0 100 95 95<br />
⎥ ⎢<br />
b<br />
⎥<br />
⎢<br />
⎥ ⎢ ⎥<br />
⎢ 0 95 100 95 ⎥ ⎢c<br />
⎥<br />
⎢<br />
⎥ ⎢ ⎥<br />
⎣ 0 95 95 100⎦ ⎣d<br />
⎦<br />
To calculate the uncertainty<br />
σ<br />
Vf<br />
values (the deviation from the mean) for each<br />
individual valley profile, the square root (SQR, square terms are always positive) must be<br />
2<br />
calculated for the V f variance values σ<br />
Vf<br />
to obtain the standard deviation σ<br />
Vf<br />
values of all<br />
valley profiles. Finally, the<br />
σ<br />
Vf<br />
values will be added to and subtracted out of the V f index<br />
values of each valley profiles to determine the effect of the assumed ASTER elevation<br />
errors on the final results and in turn establish the finals active tectonic classes and their<br />
ranges.<br />
To perform the variance-covariance error propagation analysis, MATLAB 7.0<br />
software has been employed for this purpose using the previously calculated V f results.<br />
The MATLAB command lines listed in table 4.3 explains the step-by-step procedures to<br />
181
obtain the standard deviation (i.e. σ Vf ) and the variance results of each valley profile. The<br />
MATLAB commands are color-coded whereas each set of commands are highlighted, the<br />
main command lines are black and preceded with (-) sign, instructions in green explain<br />
the MATLAB command, and instructions in red explain commands procedures where<br />
Vdata = the partial derivative calculations of ABCD (new output data), Obsdata = the V f<br />
calculations (input or observation data), Sxx = the covariance matrix, Syy = the<br />
covariance matrix of all profile ratios, Std = the standard deviation values, Columns 1 and<br />
2 = the fronts and valley profiles numbers, respectively, Columns 3 to 6 = the A, B, C,<br />
and D calculation values, respectively, Column 7 = the ABCD * Sxx * ABCD'<br />
calculation results, Column 8 = the SQR (results of the final dV f equation), and Column 9<br />
= the V f mean values for each valley profiles set related to a mountain front.<br />
Tables 4.4 to 4.7 illustrate the final V f tectonic classes and the σ Vf values that<br />
represent the final results of the ASTER accuracy equation. In addition, the final<br />
+ ) and ( V<br />
f<br />
− σ ) results for all regions within the study area are listed<br />
Vf<br />
( V<br />
f<br />
σ<br />
Vf<br />
considering the vertical accuracy ±10m and the horizontal pixel size 30m of the ASTER<br />
derived DEMs (figure 4.6). The lowest and highest final values of 0.02 and 2.25 were<br />
found in Aqaba and the Dead Sea area, respectively. Since the V f index is a ratio and its<br />
analysis normally expressed as absolute values (in this case as positive numbers),<br />
therefore, all negative values after subtracting the DEM accuracy results (σ Vf ) out of the<br />
V f values ( V<br />
f<br />
− σ ) were out of range (i.e. equal zero) and considered as class 1<br />
Vf<br />
throughout the final V f tectonic activity class classification. The presence of negative<br />
values is donated to the shallowness of the valley bottom creating small differences in the<br />
elevations of the valleys divides compared to the valley floors. This has only occurred in<br />
182
a small number of valley profiles within the JDTZ (Dead Sea = 6 profiles, North Araba =<br />
1 profile, South Araba = 4 profiles, and Aqaba = 2 profiles).<br />
01<br />
02 %% Clear data (erases previous calculations)<br />
03<br />
04 -<br />
clear abcd i vdata Sxx (abcd = partial derivative results, vdata = outputs,<br />
and Sxx = covariance matrix)<br />
05<br />
06 %% Read xls file (reading data from an Excel file)<br />
07<br />
08<br />
%reads abcd values for a single front (specify new valley by changing the range values<br />
and spreadsheet number, e.g. sheet #3 )<br />
09 - vdata = xlsread (All_Calculations' , 3, 'S180 : X187');<br />
10<br />
11 %reads observation covariance matrix (same for all valleys)<br />
12 - Sxx = xlsread (All_Calculations' , 3, 'AC13 : AF16');<br />
13<br />
14 %raw observatoins and vf calculations (different range for each valley profile data)<br />
15 - obsdata = xlsread ('All_Calculations' , 3, 'B180 : J187');<br />
16<br />
17 % covariance matrix of all profile ratios<br />
18 - Syy = abcd * Sxx * abcd’;<br />
19<br />
20 %% compute variance of each profile (numbers indicate the output table columns)<br />
21 - abcd = vdata (:, 3, 6);<br />
22 - vdata (:, 7) = diag (abcd * Sxx * abcd’);<br />
23 - vdata (:, 8) = sqrt (vdata (:, 7));<br />
24<br />
25 %% compute mean of a front<br />
26 - V f _mean = mean (obsdata (:, 9));<br />
27<br />
28 %% compute standard deviation of a front<br />
29 - V f _std = sqrt (V f _var);<br />
30 - V f _std_excel = std (obsdata (:, 9));<br />
31<br />
32 %% compute variance (V f _var) of a front assuming correlations among profiles<br />
33 - V f _var = ((obsdata (:, 9)’ – V f _mean) * Syy * (obsdata (:, 9) – V f _mean))/<br />
34 (nume1 (obsdata (:, 9)) – 1);<br />
35<br />
36 %% Draw histogram of V f (creates a histogram of each valley profile)<br />
37 - hist (obsdata (:, 9));<br />
38 - axis ([0 2 0 10])<br />
39 - grid on<br />
40<br />
41 %% Write new data to a new spreadsheet (creates a new sheet and writes the new data)<br />
42<br />
43 %xlswrite (vdata,' spreadsheet-name' , 'sheet#' , 'range ## : ##');<br />
44<br />
Table 4.3: MATLAB command lines (each set of commands are highlighted, command<br />
lines are black and start with (-), instructions in green explain the MATLAB commands,<br />
and instructions in red explain commands procedures).<br />
183
184
185
186
187
188
Figure 4.6: The tectonic activity classes of all S mf and V f based on V f +σ Vf results.<br />
189
In table 4.8, the percentages of the valleys tectonic activity classes of the study<br />
area are presented subsequent to employing the ASTER DEM error calculation results<br />
(i.e. ±σ Vf values). In all four regions of the JDTZ, a significant increase (higher<br />
percentages) of the final results are illustrated after adding the final V f accuracy test<br />
values (i.e. ±σ Vf ) to the previously calculated V f values of each individual valley profile<br />
compared to lower values (decreased percentages) when perform substituting. This<br />
indicates the importance of using both addition and subtracting values of the DEM<br />
accuracy test to determine the final tectonic activity classes in these four regions. Thus,<br />
the minimum and maximum values of this accuracy test will establish the range of the V f<br />
final tectonic classes within the JDTZ study area.<br />
4.6. Final results and tectonic activity classes<br />
Generally, the S mf results in the northern area show lower values compared to the<br />
southern area which indicates a slightly more tectonic activity in this part of the JDTZ<br />
region. However, the V f values in the northern area demonstrate a higher values in<br />
comparison with the southern area, which is primarily related to the difference in the<br />
geological setting and rock types between the two regions. The southern area, on the<br />
other hand, has more U-shaped valleys as a result of relative tectonic quiescence<br />
compared to the northern area that has largely V-shaped valleys indicating more tectonic<br />
activity. These tectonic activity results match the recorded field and historical seismic<br />
data of the region as previously illustrated in the earthquake network and active faults<br />
relationship maps (section 4.3, figures 4.3 and 4.4).<br />
190
Dead Sea (22 valleys)<br />
Class change Initial class to New class Percentage of valleys<br />
1-2 → 1 5 / 22 = 22.7%<br />
Decreased<br />
2 → 1 or (1-2) 4 / 22 = 18.2%<br />
Not changed (decreased) 13 / 22 = 59.1%<br />
Total decreased 40.9%<br />
1 → 2 or (1-2) 8 / 22 = 36.4%<br />
1-2 → 2 or 3 4 / 22 = 18.1%<br />
Increased 2 → 3 2 / 22 = 9.10%<br />
Not changed (increased) 8 / 22 = 36.4%<br />
Total increased 63.6%<br />
Not changed (increased or decreased) 5 / 22 = 22.7%<br />
North Araba (15 valleys)<br />
Class change Initial class to New class Percentage of valleys<br />
1-2 → 1 6 / 15 = 40.0%<br />
Decreased<br />
2 → 1 or (1-2) 1 / 15 = 6.70%<br />
Not changed (decreased) 8 / 15 = 35.3%<br />
Total decreased 46.7%<br />
1 → 2 or (1-2) 6 / 15 = 40.0%<br />
1-2 → 2 or 3 4 / 15 = 26.7%<br />
Increased 2 → 3 0 / 15 = 0.00%<br />
Not changed (increased) 5 / 15 = 33.3%<br />
Total increased 66.7%<br />
Not changed (increased or decreased) 2 / 15 = 13.4%<br />
South Araba (25 valleys)<br />
Class change Initial class to New class Percentage of valleys<br />
1-2 → 1 3 / 25 = 12.0%<br />
Decreased<br />
2 → 1 or (1-2) 3 / 25 = 12.0%<br />
Not changed (decreased) 19 / 25 = 76.0%<br />
Total decreased 24.0%<br />
1 → 2 or (1-2) 5 / 25 = 20.0%<br />
1-2 → 2 or 3 4 / 25 = 16.0%<br />
Increased 2 → 3 0 / 25 = 0.00%<br />
Not changed (increased) 16 / 25 = 64.0%<br />
Total increased 36.0%<br />
Not changed (increased or decreased) 12 / 25 = 48.0%<br />
Aqaba (36 valleys)<br />
Class change Initial class to New class Percentage of valleys<br />
1-2 → 1 2 / 36 = 5.60%<br />
Decreased<br />
2 → 1 or (1-2) 0 / 36 = 0.00%<br />
Not changed (decreased) 34 / 36 = 94.4%<br />
Total decreased 5.60%<br />
1 → 2 or (1-2) 2 / 36 = 5.60%<br />
1-2 → 2 or 3 1 / 36 = 2.80%<br />
Increased 2 → 3 0 / 36 = 0.00%<br />
Not changed (increased) 33 / 36 = 91.6%<br />
Total increased 8.40%<br />
Not changed (increased or decreased) 31 / 36 = 86.2%<br />
Table 4.8: Percentages change of all valleys tectonic classes after applying the ±σ Vf<br />
values.<br />
191
The final morphometric analysis of the S mf and V f indices revealed that the JDTZ<br />
is tectonically active with slightly more activity in its northern part (figure 4.7). Theses<br />
results uphold the historic and recorded earthquake data of the region where the northern<br />
part of the JDTZ has experienced more noticeable tectonic activities than its southern<br />
part. Based on the available digital data, the S mf and V f results indicate that there are two<br />
main tectonic activity classes: more active (class 1), and moderate to less active (class 2).<br />
The active class 1 S mf result ranges from 1.00 to 1.30, whereas class 2 values are > 1.30.<br />
The V f results show the possibility of having an additional less active (or inactive)<br />
tectonic class (class 3) that is still considered as a component of the moderate to less<br />
active class 2. The V f active class 1 ranges from ≤ 0.09 to 0.50, the moderate to less<br />
active class 2 ranges from 0.51 to 1.88, and the less active to inactive class 3 values are ><br />
1.88 (table 4.9).<br />
Tectonic activity classes and description S mf V f<br />
Class 1 More active 1.00 – 1.30 ≤ 0.09 – 0.50<br />
Class 2 Moderate to Less Active > 1.30 0.51 – 1.88<br />
Class 3 Less Active (inactive) - > 1.88<br />
Table 4.9: Final S mf and V f tectonic activity classes.<br />
Similar to any other digital data, the generated DEMs primarily depend on the<br />
resolution of the satellite imagery source. Thus, the better the initial ASTER imagery<br />
resolution, the more enhanced DEMs quality could be created, hence, extra accurate<br />
calculations of both S mf and V f indices. The values of S mf and V f indices analysis in the<br />
JDTZ are reasonably close to the morphometric analysis results reached by other<br />
researchers (chapter 2, table 2.1). These tectonic indices results were based on the<br />
proposed ASTER vertical accuracy of ±10m and the generated DEMs horizontal pixel<br />
size of 30m. This indicates the morphometric analysis of S mf and V f using the digital<br />
192
approach has great potential in determining the tectonic activity classes in the JDTZ<br />
study area.<br />
Figure 4.7: The active tectonic classes of the northern and southern regions of the JDTZ<br />
showing all S mf and V f +σ Vf results.<br />
193
5. Chapter Five: Conclusion<br />
5.1. Conclusion<br />
The mountain front sinuosity index (S mf ) and the ratio of valley floor width to<br />
valley height (V f ) are useful indicators of relative tectonic activity. Nevertheless, utilizing<br />
the new digital approach as presented in this research, based on satellite imagery and<br />
geographic digital data of land features, requires thorough examination and additional<br />
research. Generally, remote sensing has limitations, and to get accurate geomorphic<br />
analysis results it would be highly recommended if carried out together with ground<br />
truthing (i.e. ground referencing data) and obtaining precise GPS elevation data of the<br />
JDTZ study area.<br />
The relative 30m-DEMs of the JDTZ were successfully generated from ASTER<br />
imagery using PCI OrthoEngine software. ASTER digital data are available for many<br />
parts of the Earth for a reasonable purchase price of US $55 per scene. ASTER imagery<br />
and the derived DEMs provide good sources for mapping at scales in the range of<br />
1:100,000 and 1:50,000 and for obtaining relative details about topography and elevation<br />
information for a wide range of terrains (Kamp et al. 2003).<br />
The morphometric analysis of mountain front sinuosity and the ratio of valley<br />
floor width to valley height have proven to be useful in determining the tectonic activity<br />
of several regions of different geological settings (Chapter two, section 2.3). The results<br />
of the digital morphometric analysis approach of the S mf and V f indices in the JDTZ are<br />
consistent with the northern area been of somewhat more tectonically active than the<br />
southern area. Based on the available digital data, the S mf and V f results indicate that<br />
there are two main tectonic activity classes: more active (class 1), and moderate to less<br />
194
active (class 2). The active class 1 sinuosities (S mf ) result ranges from 1.00 to 1.30,<br />
whereas class 2 values are > 1.30. The V f index results illustrate the possibility of having<br />
an additional less active (inactive) tectonic class (class 3), but it is still considered as a<br />
component of the moderate to less active tectonic category as in class 2. The V f active<br />
class 1 ranges from ≤ 0.09 to 0.50, the moderate to less active class 2 ranges from 0.51 to<br />
1.88, and the less active class 3 values are > 1.88.<br />
Although the new digital approach has only been tested in Jordan on an arid to<br />
semi arid region, it has the potential of providing reliable results for morphometric<br />
analysis and quantifying the tectonic activity in the JDTZ study area. Indeed, further<br />
studies using the new approach are highly recommended in different places and terrains<br />
of different geological settings to examine this method’s efficiency.<br />
However, the combined data from all analysis of morphometric landscape<br />
parameters highlight significant variations in relative and numerical values of the JDTZ<br />
tectonic activity. It is critical to integrate field data in order to examine other nontectonic<br />
factors such as drainage basin size, stream power, position of fluvial systems relative to<br />
mountain fronts, and variations in bedrock and weathering processes that have their input<br />
to the variations of the overall calculations (Wells et al. 1988).<br />
In conclusion, with the available ASTER satellite imagery and the resolution of<br />
the ASTER derived DEM (30m pixel size and ±10m vertical accuracy), the digital<br />
morphometric analysis approach of mountain fronts (S mf ) and valley profiles (V f ) has the<br />
potential of providing results that are useful in determining the tectonic activity of the<br />
JDTZ study area. More accurate and reliable results could be obtained utilizing the digital<br />
195
S mf and V f indices analysis with the use of smaller DEM ground resolution of 15m to<br />
10m or less.<br />
5.2. Limitation of the Study<br />
Since this research is believed to be among the first attempts to use a digital<br />
geomorphic analysis approach for calculation of morphometric indices, the literature<br />
discussing this method was scarce and quite limited. In addition, ASTER imagery data<br />
has never been used in any previous research in Jordan, thus, the accuracy of the obtained<br />
ASTER digital data have never been tested against the various existing terrains in Jordan<br />
and the JDTZ.<br />
One of the major inadequacies in this research that would have added valuable<br />
information is the lack of digital data and comprehensive tectonic databases of Jordan.<br />
Furthermore, the absence of the large scale topographic maps (1:25,000 or larger) of the<br />
JDTZ study area hindered their comparison with the ASTER derived DEMs to perform<br />
DEM accuracy test by using a simple map algebra operator (Cuartero et al. 2004). In<br />
addition, there is a lack of ground control points (GCPs) and other elevation data such as<br />
that can be obtained by the use of differential global positioning system (GPS) method<br />
within the JDTZ study area (Chrysoulakis et al. 2004, Leick 2004, Poli et al. 2005).<br />
5.3. Future directions/remarks<br />
It has been studied that various indices have different sensitivities to specific<br />
types and rates of tectonic activity, in addition to variables such as lithology, alluvial<br />
fans, and drainage basin size (Wells et al. 1988). Moreover, both mountain front sinuosity<br />
(S mf ) and stream length-gradient index (SL) are potentially valuable reconnaissance tools<br />
used to identify areas of relative tectonic activity when jointly exploited. As a result, this<br />
196
study stresses the value of incorporating different types of landscape parameters in the<br />
JDTZ geomorphic analyses.<br />
Most of the geomorphic indices, such as the drainage basin asymmetry (AF),<br />
work best where each drainage basin is underlain by the same rock type (Keller and<br />
Pinter 2002). Therefore, conducting research focusing on analyzing several geomorphic<br />
indices in limited areas within the JDTZ might deliver significant relative tectonic<br />
activity results and may possibly expand the range of tectonic activity classes.<br />
Obtaining GPS elevation data of prominent landscape features and locations (i.e.<br />
actual GCPs) in the JDTZ are highly recommended to generate absolute DEMs of the<br />
study area in order to accurately compute the S mf and V f morphometric indices to<br />
precisely determine the tectonic activity in the JDTZ.<br />
Another point, which should be investigated in more detail, is the comparison of<br />
the new digital morphometric approach to an existing locations with known tectonic<br />
activity (i.e. activity classes) that has been determined by the morphometric analysis of<br />
landforms and topography (e.g. the Mojave Desert, California) to specify the difference<br />
in results between the two methods. In addition, this digital morphometric method in the<br />
JDTZ and other locations should be tested by using multiple DEMs produced by other<br />
sensors and of several ground resolutions.<br />
197
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Internet Resources<br />
ASTER Websites. Selected websites created by the USGS and NASA Jet Propulsion<br />
Laboratory (JPL) with complete description of the ASTER satellite instruments and<br />
imagery.<br />
http://asterweb.jpl.nasa.gov/<br />
http://eospso.gsfc.nasa.gov/<br />
http://terra.nasa.gov/<br />
http://www.terrainmap.com/rm22.html#top<br />
http://edcdaac.usgs.gov/aster/ast_l1b.asp<br />
http://edcdaac.usgs.gov/aster/ast14dem.asp<br />
http://edcdaac.usgs.gov/aster/asterprocessing.asp<br />
http://www.satimagingcorp.com/satellite-sensors/aster.html<br />
http://www.gds.aster.ersdac.or.jp/gds_www2002/index_e.html<br />
215
Appendix A<br />
Tables A.1 to A.5 list detailed results of both mountain front sinuosity (S mf ) and<br />
the valley floor width/height ratio (V f ) computations. In addition, the shape of each<br />
individual valley profile is described in an attempt to find the relationship between valley<br />
shapes and V f index results.<br />
Fronts/Valleys<br />
Location<br />
Front#<br />
Length<br />
(Km)<br />
S mf<br />
S mf<br />
Class<br />
Valley<br />
Profile#<br />
V f<br />
V f<br />
Class<br />
V f<br />
Mean<br />
V f<br />
Mean<br />
Class<br />
Dead Sea 1 67.70 1.07 1 1 1.18 2 0.54 1 U<br />
Valley<br />
Shape<br />
2 1.03 2 U<br />
3 0.51 1 - 2 U<br />
4 1.19 2 V<br />
5 0.19 1 V<br />
6 0.77 1 - 2 U<br />
7 0.47 1 V<br />
8 1.19 2 U<br />
9 0.28 1 V<br />
10 0.64 1 - 2 U<br />
11 0.47 1 V<br />
12 0.25 1 V<br />
13 0.32 1 V<br />
14 0.73 1 - 2 V<br />
15 0.18 1 V<br />
16 0.27 1 V<br />
17 0.41 1 V<br />
18 0.20 1 V<br />
19 0.36 1 V<br />
20 0.30 1 V<br />
21 0.25 1 V<br />
22 0.65 1 - 2 V<br />
Table A.1: The Dead Sea mountain front sinuosity (S mf ) and valley floor width to valley<br />
height ratio (V f ) results.<br />
216
Fronts/Valleys<br />
Location<br />
Front#<br />
Length<br />
(Km)<br />
S mf<br />
S mf<br />
Class<br />
Valley<br />
Profile#<br />
V f<br />
V f<br />
Class<br />
V f<br />
Mean<br />
V f<br />
Mean<br />
Class<br />
North Araba 1 64.63 1.21 1 1 0.38 1 0.50 1 V<br />
Valley<br />
Shape<br />
2 0.40 1 U<br />
3 0.38 1 V<br />
4 0.26 1 V<br />
5 0.34 1 V<br />
6 0.57 1 U<br />
7 0.69 1 V<br />
8 1.22 2 V<br />
9 0.85 1 V<br />
10 0.53 1 V<br />
11 0.61 1 V<br />
12 0.37 1 V<br />
13 0.26 1 V<br />
14 0.54 1 V<br />
15 0.33 1 U<br />
Table A.2: The North Araba mountain front sinuosity (S mf ) and valley floor width to<br />
valley height ratio (V f ) results.<br />
217
Fronts/Valleys<br />
Location<br />
Front#<br />
Length<br />
(Km)<br />
S mf<br />
S mf<br />
Class<br />
218<br />
Valley<br />
Profile#<br />
V f<br />
V f<br />
Class<br />
V f<br />
Mean<br />
V f<br />
Mean<br />
Class<br />
Dead Sea 1 132.32 1.14 1 1 1.18 2 0.53 1 U<br />
& North<br />
Araba<br />
2 1.03 2 U<br />
3 0.51 1 U<br />
Valley<br />
Shape<br />
4 1.19 2 V<br />
5 0.19 1 V<br />
6 0.77 1 - 2 U<br />
7 0.47 1 V<br />
8 1.19 2 U<br />
9 0.28 1 V<br />
10 0.64 1 - 2 U<br />
11 0.47 1 V<br />
12 0.25 1 V<br />
13 0.32 1 V<br />
14 0.73 1 - 2 V<br />
15 0.18 1 V<br />
16 0.27 1 V<br />
17 0.41 1 V<br />
18 0.20 1 V<br />
19 0.36 1 V<br />
20 0.30 1 V<br />
21 0.25 1 V<br />
22 0.65 1 - 2 V<br />
1 1 0.38 1 V<br />
2 0.40 1 U<br />
3 0.38 1 V<br />
4 0.26 1 V<br />
5 0.34 1 V<br />
6 0.57 1 U<br />
7 0.69 1 V<br />
8 1.22 2 V<br />
9 0.85 1 V<br />
10 0.53 1 V<br />
11 0.61 1 V<br />
12 0.37 1 V<br />
13 0.26 1 V<br />
14 0.54 1 V<br />
15 0.33 1 U<br />
Table A.3: The combined Dead Sea and North Araba mountain front sinuosity (S mf ) and valley<br />
floor width to valley height ratio (V f ) results.
Fronts/Valleys<br />
Location<br />
Front#<br />
Length<br />
(Km)<br />
S mf<br />
S mf<br />
Class<br />
Valley<br />
Profile#<br />
V f<br />
V f<br />
Class<br />
V f<br />
Mean<br />
V f<br />
Mean<br />
Class<br />
South Araba 1 35.94 1.16 1 1 0.35 1 0.56 1 V<br />
Valley<br />
Shape<br />
2 1.24 2 U<br />
22 0.29 1 V<br />
23 0.33 1 V<br />
24 0.15 1 V<br />
25 1.02 2 V<br />
2 3.62 1.21 1 3 0.58 1 0.75 1 - 2 U<br />
4 0.91 1 - 2 U<br />
3 32.14 1.28 1 5 0.53 1 0.35 1 U<br />
6 1.07 2 U<br />
7 0.79 1 - 2 U<br />
8 0.49 1 V<br />
9 0.11 1 V<br />
10 0.13 1 V<br />
11 0.21 1 V<br />
12 0.12 1 V<br />
13 0.26 1 V<br />
14 0.15 1 V<br />
15 0.41 1 U<br />
16 0.11 1 V<br />
17 0.42 1 U<br />
18 0.19 1 V<br />
19 0.29 1 V<br />
4 15.26 1.17 1 20 0.52 1 0.47 1 V<br />
21 0.42 1 V<br />
Table A.4: The South Araba mountain front sinuosity (S mf ) and valley floor width to<br />
valley height ratio (V f ) results.<br />
219
Fronts/Valleys<br />
Location<br />
Front#<br />
Length<br />
(Km)<br />
S mf<br />
S mf<br />
Class<br />
Valley<br />
Profile#<br />
V f<br />
V f<br />
Class<br />
V f<br />
Mean<br />
V f<br />
Mean<br />
Class<br />
Aqaba 1 10.52 1.12 1 1 0.17 1 0.16 1 U<br />
Valley<br />
Shape<br />
2 0.15 1 U<br />
2 14.60 1.22 1 3 0.38 1 0.32 1 U<br />
4 0.36 1 U<br />
5 0.23 1 U<br />
3 12.03 1.21 1 6 0.29 1 0.43 1 V<br />
7 0.58 1 - 2 U<br />
4 19.98 1.71 2 8 1.03 2 0.67 1 - 2 U<br />
9 1.02 2 U<br />
10 0.40 1 U<br />
11 0.24 1 U<br />
5 8.07 1.17 1 12 0.55 1 0.55 1 - 2 U<br />
6 10.12 1.07 1 13 0.15 1 0.18 1 V<br />
14 0.21 1 U<br />
7 10.62 1.22 1 15 0.07 1 0.14 1 V<br />
16 0.16 1 V<br />
17 0.18 1 U<br />
18 0.15 1 V<br />
8 21.31 1.25 1 19 0.82 1 - 2 0.26 1 U<br />
20 0.16 1 V<br />
21 0.13 1 V<br />
22 0.23 1 U<br />
23 0.19 1 V<br />
24 0.27 1 V<br />
25 0.15 1 V<br />
26 0.25 1 V<br />
27 0.25 1 U<br />
28 0.12 1 V<br />
9 22.30 1.13 1 29 0.09 1 0.21 1 V<br />
30 0.09 1 V<br />
31 0.55 1 U<br />
32 0.18 1 V<br />
33 0.40 1 U<br />
34 0.13 1 V<br />
35 0.12 1 V<br />
36 0.15 1 V<br />
Table A.5: The Aqaba mountain front sinuosity (S mf ) and valley floor width to valley<br />
height ratio (V f ) results.<br />
220