Download Volume II Accomplisments (28 Mb pdf). - IRIS

More documents

Recommendations

Info

$Refraction - IRIS$

Imaging Lithospheric Foundering beneath the Central Sierra Nevada with Receiver Functions, Teleseismic Surface Waves, and Earthquake Locations Andy Frassetto (University of Copenhagen), Hersh Gilbert (Purdue University), Owen Hurd (Stanford University), George Zandt (University of Arizona), Thomas J. Owens (University of South Carolina), Craig H. Jones (University of Colorado) The southern Sierra Nevada represents a fundamental example of a Cordilleran batholith which has recently lost its eclogitized, mafic-ultramafic lower crust and lithospheric mantle. From May 2005 through September 2007, the Sierra Nevada EarthScope Project (SNEP) targeted the central and northern Sierra Nevada with an array of broadband seismometers to characterize how lithospheric foundering relates to the Isabella and Redding deep seismic anomalies, the modern relief of the Sierra, and ongoing deformation and volcanism in eastern California. Selected key findings from our current study show evidence for ongoing foundering beneath the west-central Sierra Nevada, just southwest of Yosemite National Park. Conversions from the Moho in stacked receiver functions change from high amplitude and shallow (30-35 km depth) along the High Sierra and Walker Lane to low amplitude and deep (50-55 km) beneath the west-central foothills (Figure 1). Strong negative conversions beneath the Walker Lane, including Long Valley Caldera, are consistent with low wavespeed layering associated with partial melt. Coincidently, surface wave phase velocities show an extensive region of fast material beneath the central Sierra foothills within the lower crust and upper mantle (Figure 2). This fast anomaly merges with the Isabella Anomaly at deeper levels beneath the south-western Great Valley. Beneath the eastern portion of the Sierra, a broad slow anomaly underlies much of the Walker Lane and regions of recent volcanism, indicating the presence of asthenospheric mantle encroaching beneath the High Sierra. Earthquakes located by SNEP show two distinct trends localized along the west-central foothills and batholith. A scattered zone of seismicity lies above the region encompassing diffuse Moho. A more confined trend of earthquakes occurs near where the conversions from the Moho diminish and deepen. This seismicity includes long-period events which occasionally occur at the Moho, likely signaling magma intrusion into the lower crust. Incorporating observations from geophysical studies and xenoliths sampling the crust and upper mantle, we interpret the region of diffuse Moho and fast lower crust and upper mantle as the remaining gravitationally unstable, actively foundering root of the central Sierra Nevada batholith. The region of slow upper mantle phase velocities and sharp Moho demarcates the region where the batholithic root has been removed. References Zandt, G., Gilbert, H., Owens, T.J., Ducea, M., Saleeby, J., and Jones, C.H., 2004, Active foundering of a continental arc root beneath the southern Sierra Nevada in California, Nature, 431, 41–46. Acknowledgements: This work was supported by the National Science Foundation’s EarthScope grants EAR-0454554, EAR-0454524, and EAR- 0454535 to the Universities of Arizona, Colorado, and South Carolina. This work was also made possible by funding from the National Science Foundation through the Graduate Research Fellowship Program. Figure 1: Interpreted common-conversion-point stack of receiver functions from broadband stations (blue) deployed across the central Sierra Nevada. Red represents strong conversions off the up-going P-wave from high-to-low steps in wavespeed; blue represents low-to-high steps. Locations of nearby earthquakes are projected onto the profile. White circles denote long period earthquakes. GV = Great Valley, SNB = Sierra Nevada batholith, WL = Walker Lane. The transect is shown in map view in Figure 2. Figure 2: Phase velocities for 30 second (left) and 67 second (right) period teleseismic surface waves. Shading ranges from pink (>4.2 km/s) to red (
The Isabella Anomaly Imaged by Earthquake and Ambient Noise Rayleigh Wave Dispersion Data: A Composite Anomaly of Sierra Nevada Batholith Root Foundering and Pacific Plate Slab-Flap Translation? Josh Stachnik (Univ. Wyoming), Ken Dueker (Univ. of Wyoming), Hersh Gilbert (Purdue Univ.), George Zandt (Univ. of Arizona) Sierra Nevada Earthscope Project (SNEP) and Earthscope Transportable Array (TA) Rayleigh wave dispersion data are inverted to construct a shear velocity model of the Sierra Nevada and San Joaquin valley. The Rayleigh wave dispersion dataset was measured using the two-plane wave method with earthquake records and the parametric Bessel-zeros method [Ekstrom et al., 2009] with correlated ambient noise records. Two starting velocity models have been tested: a uniform (4.4 km/s) starting model and a starting model with the Moho mapped by Pn station time terms [Buehler and Shearer, in review]. With respect to previous body and surface wave tomograms, the Isabella anomaly is imaged as more geometrically rich. This observation leads us to consider a composite explanation of the anomaly as a Pacific plate slab-flap (Monterey microplate) and the foundering roots of the southern Sierra Nevada batholith. The slab flap is identified as a 4.4- 4.6 km/s NW-SE striking 140 km wide planar anomaly imaged at 60-110 km depth beneath the San Joaquin valley. The foundering southern Sierra batholithic root is identified as an N-S trending 4.4-4.5 km/s high velocity region beneath the southern Sierran foothills. This anomaly is bowed down beneath the high standing southern Sierra block to form a wedge filled with 4.2 km/s mantle which is interpreted as in-flowed asthenosphere. The pros and cons of this composite interpretation will be discussed. Comparison of our velocity model with the only other joint ambient/earthquake surface wave model [Moschetti et al., in review] finds that the two models are well correlated. Comparison of our velocity model with teleseismic body wave tomograms reveals substantial differences in the geometry and depth extent of the Isabella anomaly related to differences in the resolution of surface and body waves. References Shear velocity image from inversio of ambient and earthquake Rayleigh wave dispersion measurements using SNEP and Transportable array data. Ekström, G., G. A. Abers,and S. C. Webb, Determination of surface-wave phase velocities across USArray from noise and Aki's spectra formulation, Geophys. Res. Lett., 36, L18301, 2009. 2010 IRIS Core Programs Proposal | Volume II | Upper Mantle Structure and Dynamics | II-205
Page 1 and 2:
volume ii - accomplishments Facilit
Page 3 and 4:
volume ii - accomplishments Facilit
Page 5 and 6:
CONTENTS Introduction..............
Page 7 and 8:
Non-Volcanic Tremor along the Oaxac
Page 9 and 10:
Detecting the Limit of Slab Break-o
Page 11:
Lower Mantle, Core-Mantle Boundary
Page 14 and 15:
• Non-Earthquake Seismic Sources
Page 16 and 17:
acoustics community by permitting a
Page 18 and 19:
Near-Surface Environments - Hazards
Page 20 and 21:
Why Do Faults Slip? Emily Brodsky (
Page 22 and 23:
Another probe of fault evolution is
Page 24 and 25:
to provide a best match with the Gl
Page 26 and 27:
tectonic disruption and mass accumu
Page 28 and 29:
W3 ∆ 5 . A number of intriguing r
Page 30 and 31:
thermal and compositional effects r
Page 33 and 34:
Towards a Global School Seismic Net
Page 35 and 36:
On-Line Seismology Curriculum for U
Page 37 and 38:
Teachers on the Leading Edge: Earth
Page 39 and 40:
USArray Education and Outreach in S
Page 41 and 42:
From an IRIS Lecture Tour to a Gene
Page 43 and 44:
Explorer Series Robert Bartolotta (
Page 45 and 46:
Workshop “Earth System Science fo
Page 47 and 48:
The IRIS Internship Cycle: From Int
Page 49 and 50:
Community-Outreach Efforts in Data
Page 51 and 52:
Site Reconnaissance for Earthscope
Page 53 and 54:
jAmaseis: Seismology Software Meeti
Page 55 and 56:
Near Real-Time Simulations of Globa
Page 57 and 58:
FuncLab: A MATLAB Interactive Toolb
Page 59 and 60:
Five Years of Distributing the Seis
Page 61 and 62:
IRIS DMS Data Products, Beyond Raw
Page 63 and 64:
Local Earthquakes in the Dallas-Ft.
Page 65 and 66:
Epicentral Location Based on Raylei
Page 67 and 68:
Analysis of Spatial and Temporal Se
Page 69 and 70:
Exceptional Ground Motions from the
Page 71 and 72:
The 2010 Mw7.2 El Mayor-Cucapah Ear
Page 73 and 74:
Effects of Kinematic Constraints on
Page 75 and 76:
Imaging of the Source Properties of
Page 77 and 78:
Teleseismic Inversion for Rupture P
Page 79 and 80:
The Global Aftershocks of the 2004
Page 81 and 82:
The 17 July 2006 Java Tsunami Earth
Page 83 and 84:
Seismic Cycles on Oceanic Transform
Page 85 and 86:
Migration of Early Aftershocks Foll
Page 87 and 88:
Apparent Stress Variations at the O
Page 89 and 90:
Automated Identification of Telesei
Page 91 and 92:
Evaluating Ground Motion Prediction
Page 93 and 94:
Tremor Monitoring Aaron Wech (Unive
Page 95 and 96:
Slow Slip and Tremor in the Norther
Page 97 and 98:
0 0.5 1 1.5 2 2.5 3 0 0.5 1 1.5 2 2
Page 99 and 100:
Intimate Details of Tremor Observed
Page 101 and 102:
Global Search of Triggered Tremor a
Page 103 and 104:
Slab Morphology in the Cascadia For
Page 105 and 106:
Source Analysis of the Memorial Day
Page 107 and 108:
Iceberg Tremor and Ocean Signals Ob
Page 109 and 110:
Elucidating the Stick-Slip Nature o
Page 111 and 112:
Probing the Atmosphere and Atmosphe
Page 113 and 114:
Volcanic Plume Height Measured by S
Page 115 and 116:
Eruption Dynamics at Mount St. Hele
Page 117 and 118:
A Search for the Lunar Core Using A
Page 119 and 120:
Seismic Imaging of the Mt. Rose Fau
Page 121 and 122:
Structure of the California Coast R
Page 123 and 124:
Temporal Variations in Crustal Scat
Page 125 and 126:
High-Resolution Locations of Trigge
Page 127 and 128:
Adjoint Tomography of the Southern
Page 129 and 130:
Crustal Structure of the High Lava
Page 131 and 132:
Controlled Source Seismic Experimen
Page 133 and 134:
Structural Interpretations Based on
Page 135 and 136:
Optimized Velocities and Prestack D
Page 137 and 138:
40 Crustal Structure beneath the Hi
Page 139 and 140:
Controlled-Source Seismic Investiga
Page 141 and 142:
Northward Thinning of Tibetan Crust
Page 143 and 144:
An Integrated Analysis of an Ancien
Page 145 and 146:
Crustal Velocity Structure of Turke
Page 147 and 148:
Ambient Noise Tomography of the Pam
Page 149 and 150:
Ambient Noise Monitoring of Seismic
Page 151 and 152:
Mushy Magma beneath Yellowstone Ris
Page 153 and 154:
Imaging the Seattle Basin to Improv
Page 155 and 156:
Developing a Database of ENA Ground
Page 157 and 158:
Lithospheric Layering in the North
Page 159 and 160:
eflective zones on depthmigrated se
Page 161 and 162:
FischerFig05.pdf 1 2/8/10 12:31 PM
Page 163 and 164:
S-Velocity Structure of Cratons, fr
Page 165 and 166: Seismic Structure of the Crust and
Page 167 and 168: Subducted Oceanic Asthenosphere and
Page 169 and 170: Detecting the Limit of Slab Break-o
Page 171 and 172: Pn Tomography of the Western United
Page 173 and 174: 3-D Isotropic Shear Velocity Model
Page 175 and 176: Seismic Anisotropy Associated with
Page 177 and 178: Anisotropy in the Great Basin from
Page 179 and 180: Source-Side Shear Wave Splitting an
Page 181 and 182: S-Velocity Structure of the Upper M
Page 183 and 184: Velocity Structure of the Western U
Page 185 and 186: Segmented African Lithosphere benea
Page 187 and 188: Imaging the Mantle Wedge in the Cen
Page 189 and 190: A Slab Remnant beneath the Gulf of
Page 191 and 192: Imaging the Southern Alaska Subduct
Page 193 and 194: Opposing Slabs under Northern South
Page 195 and 196: Effect of Prior Petrological Constr
Page 197 and 198: Global Azimuthal Seismic Anisotropy
Page 199 and 200: The Stratification of Seismic Azimu
Page 201 and 202: Upper Mantle Anisotropy beneath the
Page 203 and 204: The Teleseismic Signature of Fossil
Page 205 and 206: Seismic Anisotropy under Central Al
Page 207 and 208: Stress-Induced Upper Crustal Anisot
Page 209 and 210: Tau-p Depropagation of Five Regiona
Page 211 and 212: Mapping the Upper Mantle with the S
Page 213 and 214: Upper Mantle Structure of Southern
Page 215: The Africa-Europe Plate Boundary in
Page 219 and 220: Tomographic Image of the Crust and
Page 221 and 222: Small-Scale Mantle Heterogeneity an
Page 223 and 224: Mantle Heterogeneity West and East
Page 225 and 226: New Geophysical Insight into the Or
Page 227 and 228: The Plume-slab Interaction beneath
Page 229 and 230: Imaging the Shear Wave Velocity "Pl
Page 231 and 232: Slab Fragmentation and Edge Flow: I
Page 233 and 234: Mantle Shear-Wave Velocity Structur
Page 235 and 236: Discordant Contrasts of P- and S-Wa
Page 237 and 238: Upper Mantle Discontinuity Topograp
Page 239 and 240: Edge-Driven Convection beneath the
Page 241 and 242: Imaging Attenuation in the Upper Ma
Page 243 and 244: Three-Dimensional Electrical Conduc
Page 245 and 246: Core-Mantle Boundary Heat Flow Thor
Page 247 and 248: Constraints on Lowermost Mantle Ani
Page 249 and 250: Localized Double-Array Stacking Ana
Page 251 and 252: Waveform Modeling of D" Discontinui
Page 253 and 254: Absence of Ultra-Low Velocity Zones
Page 255 and 256: Moving Seismic Tomography Beyond Fa
Page 257 and 258: A Three-Dimensional Radially Anisot
Page 259 and 260: The Importance of Crustal Correctio
Page 261 and 262: Slabs Do Not Go Gentle Karin Sigloc
Page 263 and 264: Localized Temporal Change of the Ea
Page 265 and 266: Core Structure Reexamined Using New
Page 267 and 268:
Large Variations in Travel Times of
Page 269 and 270:
Observations of Antipodal PKIIKP Wa
Page 271 and 272:
Regional Variation of Inner Core An
Page 273:
Wide-Scale Detection of Earthquake
show all

Download Volume II Accomplisments (28 Mb pdf). - IRIS

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?