title of the thesis - Department of Geology - Queen's University

THE INFLUENCES OF STRESS AND STRUCTURE ON MINING- 

INDUCED SEISMICITY IN CREIGHTON MINE, SUDBURY, CANADA 

by 

Paige Erin Snelling 

A thesis submitted to the Department of Geological Sciences and Geological Engineering 

In conformity with the requirements for 

the degree of Master of Science (Engineering) 

Queen’s University 

Kingston, Ontario, Canada 

(September, 2009) 

Copyright © Paige Erin Snelling, 2009

Abstract 

The Creighton Mine is a structurally complex and seismically active mining environment. 

Microseismic activity occurs daily and increases with depth, complicating downward mine 

expansion. Larger magnitude events occur less frequently but can damage mine infrastructure, 

interrupt operations and threaten worker safety. This thesis explores the relationships between 

geological structure and mining-induced seismicity through geological, seismological and 

numerical modelling investigations in an area known as the Creighton Deep, with concentration 

on the 7400 Level (2255 m). 

Geological features within the Creighton Deep have a reported association with seismic activity. 

Four families of shear zones were identified during field investigations, the most prominent 

striking SW and steeply dipping NW. 

Seismicity from 2006-2007 is analyzed. Spatial and temporal trends and seismic event 

parameters show little correlation to shear zone geometry. Instead, seismic event parameters 

correlate to spatial clusters of events. A remote cluster of events to the southwest of the 

excavation exhibits anomalously high seismic parameter values. This area of the mine continues 

to be a source of elevated seismicity. 

Fault plane solutions are utilized to compare shear zone geometry with active slip surfaces. 

Solutions for macroseismic events are inconsistent, while microseismic event focal mechanisms 

have similar pressure, tension and null axes. The resulting solutions do not align with shear-zone 

orientations. A stress inversion using microseismic focal mechanism information yields a stress 

tensor that is comparable to the regional stress tensor. 

Universal Distinct Element Code numerical models demonstrate that a yield zone exists 

immediately surrounding the excavation. SW-striking shear zones modify the stress field, 

ii

esulting in increased stress to the southeast of the excavation. These high-stress zones are areas 

of preferred seismic activity. Slip is induced on select SW-striking shear zones to the south of the 

excavation as well as localized yielding. 

The characteristics of mining-induced seismicity do not correlate to shear zones. Seismicity does 

compare to modelled stress: the yielded rock mass adjacent to the excavation has little 

seismicity; areas of high stress are areas of rock mass damage and dense seismic activity. It is 

thus proposed that seismicity in the Creighton Deep results from stress-induced rock mass 

degradation rather than fault-slip. 

iii

Acknowledgements 

First and foremost I would like to thank Laurent Godin and Steve McKinnon for their guidance, 

discussions and revisions throughout the duration of this project. I am grateful for having been 

given the opportunity to explore my varied interests. 

I would like to acknowledge Vale Inco and Creighton Mine for financially supporting this 

project. I am very appreciative of the hospitality provided by the staff at Creighton Mine. I would 

like to thank Dave Andrews and John Townend for coordinating this project, Keith Seidler for his 

direction (and sense of direction) underground, Chris Meandro and the others in the Geology 

Department as well as those in Ground Control. 

I would also like to acknowledge the Engineering Seismology Group (ESG Solutions) for kindly 

donating the software necessary to complete my studies. 

I am thankful to friends, staff and colleagues in the Department of Geological Engineering and 

Geological Sciences. 

In particular I would like to thank Alan Baird who provided help with 

UDEC and FISH and many valuable discussions on stress and seismicity; Savka Dineva who 

offered seismological discussions, revisions and help with stress inversion; and Mark Diederichs 

for modelling discussions and advice. 

I offer a special thanks to my mom, Barb Halyk, and to my family who worried about me while I 

was kilometers underground. I’m ok. 

iv

Table of Contents 

Abstract..........................................................................................................................................ii 

Acknowledgements ......................................................................................................................iv 

Table of Contents .......................................................................................................................... v 

List of Figures...............................................................................................................................ix 

List of Tables ............................................................................................................................... xv 

Table of Symbols and Abbreviations .......................................................................................xvi 

Chapter 1: Introduction .............................................................................................................. 1 

1.1 Background ........................................................................................................................ 1 

1.2 Organization of Thesis ....................................................................................................... 4 

Chapter 2: Geological Assessment of Creighton Mine ............................................................. 5 

2.1 Regional Geology of the Sudbury Basin ............................................................................ 5 

2.1.1 Evolution of the Sudbury Basin................................................................................ 6 

2.1.2 Dykes ........................................................................................................................ 8 

2.1.3 Regional Faults ......................................................................................................... 8 

2.2 Local Geology of Creighton Mine ................................................................................... 11 

2.3 Mine-Scale Faults............................................................................................................. 14 

2.3.1 Footwall Shear Zone............................................................................................... 18 

2.3.2 1290 Shear Zone ..................................................................................................... 20 

2.3.3 400-East Shear Zone............................................................................................... 22 

2.3.4 Northwest Shear Zone............................................................................................. 23 

2.3.5 Return Air Raise Shear Zone .................................................................................. 24 

2.3.6 402 Shear Zone ....................................................................................................... 26 

2.3.7 Plum Shear Zone .................................................................................................... 26 

2.3.8 Fresh Air Raise Shear Zone .................................................................................... 28 

2.3.9 Fresh Air Raise-type Shear Zone............................................................................ 29 

2.3.10 Splays and minor shear zones ............................................................................... 31 

2.3.11 Late-Stage Fractures ............................................................................................. 33 

2.4 Discussion: Fault Reactivation........................................................................................ 34 

2.4.1 Geometric and kinematic summary ........................................................................ 34 

2.4.2 Evolving Stress Systems in the Sudbury Basin ...................................................... 36 

v

Chapter 3: Mining-induced Seismicity .................................................................................... 40 

3.1 Creighton Mine Seismic Monitoring System ................................................................... 40 

3.2 Event Characterization and Classification........................................................................ 41 

3.2.1 Seismic Event Parameters....................................................................................... 42 

3.2.1.1 Moment Magnitude (M)............................................................................. 43 

3.2.1.2 Seismic Energy (E o ) and Seismic Moment (M o )........................................ 45 

3.2.1.3 Energy Ratio, E s /E p .................................................................................... 46 

3.2.1.4 Stress Parameters ....................................................................................... 47 

3.2.1.5 Source Dimensions .................................................................................... 47 

3.2.1.6 Peak Acceleration Parameter, Velocity Parameter and 

Maximum Displacement ........................................................................................ 48 

3.2.2 Spatial and Temporal Event Clustering .................................................................. 48 

3.2.3 Cluster Analysis for the 7400 Level ....................................................................... 52 

3.2.4 Seismicity and Rockmass Degradation................................................................... 55 

3.3 Focal Mechanisms............................................................................................................ 58 

3.3.1 Fault Plane Solutions .............................................................................................. 58 

3.3.1.1 Fault plane solutions for macroseismic events........................................... 60 

3.3.1.2 Fault plane solutions for microseismic events ........................................... 62 

3.3.1.3 Fault Plane Solution Discussion................................................................. 66 

3.4 Stress Tensor Inversion .................................................................................................... 70 

3.4.1 Stress Tensor Discussion ........................................................................................ 74 

Chapter 4: Modelling Stress in the Creighton Deep............................................................... 78 

4.1 Introduction ...................................................................................................................... 78 

4.2 Numerical Methods .......................................................................................................... 79 

4.3 Model Input Parameters ................................................................................................... 80 

4.3.1 Elastic and Plastic Models ...................................................................................... 80 

4.3.2 Model Constituents and Input Parameters .............................................................. 81 

4.4 Modelling with a Homogeneous Stress Field................................................................... 85 

4.4.1 Case 1: Variable Fault Parameters......................................................................... 85 

4.4.2 Case 2: Variable Fault Strength by Shear Zone Family......................................... 89 

4.4.3 Case 3: Increase Principal Stress Ratio.................................................................. 92 

4.5 Tectonic Loading Model .................................................................................................. 94 

4.6 Modelling Rock Mass Degradation.................................................................................. 96 

vi

4.6.1 Fracture Reactivation.............................................................................................. 97 

4.6.2 Crack Initiation ....................................................................................................... 99 

4.7 Modelling Summary and Discussion.............................................................................. 101 

4.7.1 Synthesis: Stress, Seismicity and Structure ......................................................... 102 

4.7.2 Model Limitations................................................................................................. 104 

Chapter 5: Conclusions and Recommendations ................................................................... 106 

5.1 Summary ........................................................................................................................ 106 

5.2 Conclusions .................................................................................................................... 107 

5.3 Recommendations .......................................................................................................... 109 

References.................................................................................................................................. 111 

Appendix A: Geological Maps and Sample Locations........................................................... 117 

A.1: Site Locations.............................................................................................................. 117 

A.2: Level Plans with Sample Locations ............................................................................ 119 

Appendix B: Seismic Event Parameters ................................................................................ 126 

B.1: Event Population Statistics for the Creighton Deep .................................................... 126 

B.2: Spatial Distribution of Seismic Event Parameters for the 7400 Level ........................ 131 

B.3: Cluster Statistics .......................................................................................................... 138 

B.4: Temporal Distribution of Seismic Event Parameters .................................................. 140 

Appendix C: Fault Plane Solutions ........................................................................................ 154 

C.1: Fault Plane Solution Data for 7400 and 7530 Levels, 

January 1, 2006 – December 31............................................................................................ 154 

Appendix D: Phase 2 Models..................................................................................................... 162 

D.1: UDEC Modelling Results............................................................................................ 162 

D.1.1: Case 1 Models...................................................................................................... 163 

D.1.2: Case 2 Models...................................................................................................... 171 

D.1.3: Case 3 Models...................................................................................................... 173 

D.1.4: Tectonic Loading Models .................................................................................... 175 

D.1: Discussion of Phase 2 Models....................................................................................... 177 

D.1.1: Model Constituents ............................................................................................. 177 

D.1.2: Boundary Conditions .......................................................................................... 178 

D.2: Phase 2 Modelling Results............................................................................................ 179 

vii

D.3 Comparison of Phase 2 and UDEC Modelling Results.................................................. 184 

D.3.1 Similarities ........................................................................................................... 184 

D.3.2 Differences........................................................................................................... 185 

Appendix E: UDEC Code........................................................................................................ 186 

E.1: Case 1: Variable fault strength parameters (Elastic model)........................................ 186 

E.2: Case 1: Variable fault strength parameters (Plastic model)........................................ 188 

E.3: Case 2: Variable Fault Strength by Shear Zone Family (Elastic Model).................... 190 

E.4: Case 2: Variable Fault Strength by Shear Zone Family (Plastic Model).................... 192 

E.5: Case 3: Increased Principal Stress Ratio (Elastic Model)........................................... 194 

E.6: Case 3: Increased Principal Stress Ratio (Plastic Model)........................................... 196 

E.7: Tectonic Loading Model (Elastic Model).................................................................... 198 

E.8: Tectonic Loading Model (Plastic Model) .................................................................... 200 

E.9: S3:S1 Model for fracture reactivation.......................................................................... 203 

E.9.1: FISH Routine: ratio s3s1.fis ............................................................................... 205 

Appendix F: Fracture Reactivation........................................................................................ 206 

F.1: Derivation of Minimum-to-Maximum Principal Stress Ratio ..................................... 206 

F.2: Definitions for Deviatoric and Differential Stress ....................................................... 208 

viii

List of Figures 

Figure 1.1: Location of Sudbury and Creighton Mine...................................................................3 

Figure 2.1: (A) Location map of Sudbury in Ontario, Canada (B); the location of the 

Sudbury and surrounding tectonic provinces ............................................................5 

Figure 2.2: Local geology map. ...................................................................................................10 

Figure 2.3: Horizontal view of a fault jog in proximity to Creighton Fault.................................10 

Figure 2.4:Cross-section of Creighton Mine showing geometry of footwall and 

hangingwall rocks as well as orebodies....................................................................12 

Figure 2.5: Representative level plan for the Creighton Deep....................................................15 

Figure 2.6: Images of the Footwall Shear...................................................................................19 

Figure 2.7: (A) The 1290 Shear Zone fabric; (B) 1290 Shear Zone on the 6400 Level; 

and (C) biotite, quartz and calcite fabric of the 1290 shear zone. ............................21 

Figure 2.8: Images of the 400-East Shear Zone..........................................................................23 

Figure 2.9: (A) Photograph of the cracked concrete pad floor along the Return Air Raise 

Shear Zone on 7530L; (B) cracked shotcrete on wall of 7530L; (C) thin 

section of shear zone fabric on 7680L; (D) thin section of shear zone fabric 

on 7400 the Level.....................................................................................................25 

Figure 2.10: Reactivated structures in proximity to the Plum Shear Zone ..................................27 

Figure 2.11: Thin sections of the Fresh Air Raise Shear .............................................................29 

Figure 2.12: Images of the Fresh Air Raise-Type Shear..............................................................30 

Figure 2.13: Images of the Grizzly Splay. ...................................................................................32 

Figure 2.14: Shallow shear fractures in Creighton Deep. ............................................................33 

Figure 2.15: Block model depicting paleokinematics of mine-scale faults in the Creighton 

Deep .........................................................................................................................34 

Figure 2.16: Riedel Model of 1290 and 118-System shear zones................................................38 

Figure 2.17: NW-SE Penokean compression...............................................................................38 

Figure 3.1: Plan view of events related to development blasts production blast-induced 

events........................................................................................................................42 

Figure 3.2: Distribution of Microseismic Event Magnitudes between January 1, 2006 and 

December 31, 2007 recorded between 7000 and 7600 feet depth............................44 

ix

Figure 3.3: Frequency Magnitude Relation for events recorded between 7000 and 7600 

feet during the January 2006-December 2007 period ..............................................44 

Figure 3.4: Map of the 7400 Level showing the distribution microseismic event energy...........45 

Figure 3.5: Es/Ep ratios measured for events and blasts. The cut-off of 5 is shown by the 

dashed line................................................................................................................46 

Figure 3.6: (A) Distribution of macroseismic events surrounding 7400 Level. (B) 

Distribution of microseismic events surrounding 7400 Level. ...............................50 

Figure 3.7: Seismicity corresponding to levels 7200, 7400 and 7530 respectively.....................51 

Figure 3.8: Three clusters are isolated for events between January 1, 2006 and December 

31, 2007 located about the 7400 Level.....................................................................54 

Figure 3.9: Schematic depicting location of (A) Yield Zone, (B) Damage Zone and (C) 

Intact Zone................................................................................................................56 

Figure 3.10: Block model of a shear-slip event and corresponding focal mechanism and 

waveforms. ...............................................................................................................59 

Figure 3.11: Coupled forces along fault and auxiliary planes; paired force couples 

(double-couple); and resultant fault plane solution. .................................................59 

Figure 3.12: Lower hemisphere equal area stereonet diagram depicting the orientation of 

(A) P-axes for macroseismic fault plane solutions; (B) T-axes for the same 

events........................................................................................................................61 

Figure 3.13: Lower hemisphere equal area stereonet diagram depicting (A) Possible fault 

planes and (B) poles to planes for 93 mechanisms (186 planes and poles) for 

the 7400 Level..........................................................................................................61 

Figure 3.14: Sample fault plane solutions for macroseismic events corresponding to the 

7400 Level, January – December 2007... .................................................................62 

Figure 3.15: Contoured focal mechanism axes for the 7400 and 7530 Level..............................64 

Figure 3.16: Classification of principal event mechanism type, levels 7400 and 7530...............65 

Figure 3.17: Approximate representative focal plane solution and corresponding fault 

plane solution kinematics based on average P- and T-axis orientations. .................65 

Figure 3.18: Contoured P-axis, B-axis and T-axis orientations for events within Cluster 1. ......67 

Figure 3.19: Contoured P-axis, B-axis and T-axis orientations for events within Cluster 2. ......68 

Figure 3.20: Distribution of event mechanism types ...................................................................69 

Figure 3.21: Results of focal mechanism stress inversion. ..........................................................72 

Figure 3.22: Stress inversion for Cluster 2 focal mechanisms.....................................................72 

x

Figure 3.23: Preliminary stress inversion for Cluster 1 focal mechanisms..................................73 

Figure 3.24: Secondary stress inversion for Cluster 1 focal mechanisms....................................73 

Figure 3.25: Equal area stereonet showing proximity of principal stress orientations 

calculated from fault plane solutions to stress orientations derived from 

measured and calculated stresses .............................................................................75 

Figure 3.26: Equal area stereonet showing stress measurements. ...............................................75 

Figure 3.27: Principal stress orientations derived from stress inversion superimposed on 

contoured axis measurements...................................................................................77 

Figure 4.1: Schematic diagram of elements and nodes. ..............................................................79 

Figure 4.2: The stress-strain model for an elastic, perfectly plastic material...............................81 

Figure 4.3: Complete model geometry.. ......................................................................................82 

Figure 4.4: Mohr circle and Mohr-Coulomb failure envelope defined by cohesion and 

angle of internal friction...........................................................................................83 

Figure 4.5: Model for tectonic loading. .......................................................................................85 

Figure 4.6: Model of maximum stress for Case 1........................................................................88 

Figure 4.7: Model of differential stress for Case 1 ......................................................................88 

Figure 4.8: Model of fault slip for Case 1....................................................................................88 

Figure 4.9: Model of yielding for Case 1.....................................................................................89 

Figure 4.10: Model of maximum stress for Case 2......................................................................90 

Figure 4.11: Model of differential stress for Case 2. ...................................................................91 

Figure 4.12: Model of fault slip for Case 2..................................................................................91 

Figure 4.13: Model of yielding for Case 2...................................................................................91 

Figure 4.14: Model of maximum stress for Case 3......................................................................93 

Figure 4.15: Model of differential stress for Case 3. ...................................................................93 

Figure 4.16: Model of fault slip for Case 3..................................................................................93 

Figure 4.17: Model of yielding for Case 3...................................................................................94 

Figure 4.18: Maximum stress for tectonic model. .......................................................................95 

Figure 4.19: Differential stress for tectonic model .....................................................................95 

xi

Figure 4.20: Modelled slip for tectonic model.............................................................................95 

Figure 4.21: Tectonic model of yielding......................................................................................96 

Figure 4.22: Ratio of minimum-to-maximum principal stress.....................................................98 

Figure 4.23: Contoured domains of slip on cohesionless fractures at different angles of 

internal friction.........................................................................................................99 

Figure 4.24: Fracture initiation thresholds mapped using maximum and differential stress 

conditions. ..............................................................................................................101 

Figure 4.25: Comparison of stress and seismicity. ....................................................................104 

Figure A1: Plan view of 7000 Level..........................................................................................119 






Figure A7: Plan view of 7940 Ramp .........................................................................................125 

Figure B1: Energy-Moment relation..........................................................................................128 

Figure B2: Magnitude-frequency relation..................................................................................128 

Figure B3: Events within Creighton Mine increase with Depth................................................129 

Figure B4: Events within the Creighton Deep study area consists of mostly microseismic 

events (89.4%), blasts (9.4%) and few macroseismic events (1.2%).....................129 

Figure B5: Event frequency by month.......................................................................................130 

Figure B6: Event Frequency is plotted by hour.. .......................................................................130 

Figure B7: Events between Jan 1, 2006 and Dec 31 2007 pertaining to the 7400 Level, 

coloured by magnitude ...........................................................................................131 

Figure B8: Events between Jan 1, 2006 and Dec 31 2007 pertaining to the 7400 Level 

coloured by the number of phones used in recording.............................................131 


coloured by Seismic Energy (Log scale used). ......................................................132 


coloured by Seismic Moment (Log scale used). ....................................................132 

xii


coloured by dynamic stress drop (Log scale used).................................................133 


coloured by static stress drop (Log scale used)......................................................133 


coloured by static stress drop (Log scale used)......................................................134 


coloured by peak particle velocity (Log scale used). .............................................134 


coloured by peak particle acceleration (Log scale used)........................................135 


coloured by maximum particle displacement (Log scale used). ............................135 


coloured by source radius ......................................................................................136 


coloured by asperity radius ....................................................................................136 


coloured by location error. Events that locate outside the network to the 

north have a greater location error. ........................................................................137 

Figure B20: Magnitude-Frequency relations for (A) Cluster 1; (B) Cluster 2; and (C) 

Cluster 3. ................................................................................................................153 

Figure D1: Case 1, elastic models showing maximum stress. ..................................................163 

Figure D2: Case 1, elastic models showing differential stress...................................................164 

Figure D3: Case 1, elastic models shear displacement along discontinuities ............................165 

Figure D4: Case 1, plastic models showing major principal stress............................................166 

Figure D5: Case 1, plastic models showing differential stress ..................................................167 

Figure D6: Case 1, plastic model showing yielding ..................................................................168 

Figure D7: Case 1, plastic models showing shear displacement along discontinuities .............169 

Figure D8: Stress distribution of elastic model..........................................................................170 

Figure D9: Stress distribution of plastic model .........................................................................170 

Figure D10: Case 2, elastic models for C=0, Φ =35º.................................................................171 

Figure D11: Case 2, plastic models for C=0, Φ =35º ................................................................172 

xiii

Figure D12: Case 3 (k=2), elastic models for C=0, Φ =35º.......................................................173 

Figure D13: Case 3 (k=2), plastic models for C=0, Φ =35º.......................................................174 

Figure D14: Tectonic model, elastic models for C=0, Φ =35º...................................................175 

Figure D15: Tectonic model, plastic model for C=0, Φ =35º....................................................176 

Figure D16: Phase2 model depicting model and boundary conditions......................................178 

Figure D17: Elastic models for the 7200 Level. ........................................................................181 

Figure D18: Elastic models for the 7400 Level. .......................................................................182 

Figure D19: Elastic models for the 7530 Level. .......................................................................183 

Figure D20: Rock mass states of degradation, as modelled for the 7400 Level in Phase2. ......184 

Figure F1: Mohr-Coulomb failure envelope with Mohr circle depicting angles and 

quantities used in derivation...................................................................................206 

xiv

List of Tables 

Table 2.1: Geological Events in the Sudbury Area.......................................................................7 

Table 2.2: Fault systems within the Creighton Deep ..................................................................15 

Table 2.3: Summary of Fault Characteristics..............................................................................17 

Table 2.4: Summary of Proterozoic tectonic events ...................................................................37 

Table 3.1: Event characteristics in an intact and fractured rock mass ........................................53 

Table 3.2: Spatial cluster positions .............................................................................................54 

Table 3.3: Summary of relevant parameter mean values and standard.......................................55 

Table 3.4: Comparison of maximum principal stress orientations from various sources ...........74 

Table 4.1: Rock mass and discontinuity model properties .........................................................84 

Table 4.2: Fault parameters tested for Case 1.............................................................................86 

Table 4.3: Strength parameters assigned to shear families for Case 2........................................90 

Table A1: Summary of site visit locations, oriented samples and thin sections .......................117 

Table B1: Summary Statistics for microseismic, macroseismic and blast events ....................126 

Table B2: Summary Statistics for microseismic event clusters. .............................................138 

Table C1: Fault Plane Solution Data for 7400 and 7530 Levels...............................................154 

xv

Table of Symbols and Abbreviations 

Symbol Explanation 

∆σ Static stress drop (Pa) 

μ Shear modulus (microseismic analysis) 

υ Poisson’s ratio 

Ø Angle of internal friction (°) 

ρ Density (kg/m 3 ) 

σ 1 Maximum principal stress 

σ 2 Intermediate principal stress 

σ 3 Minimum principal stress 

σ a Apparent stress (Pa) 

σ d Dynamic stress drop (Pa) 

σ n Normal stress (MPa) 

σ UCS Uniaxial compressive strength 

τ Shear stress (MPa) 

Bt Biotite 

C Cohesion 

Cal Calcite 

Chl Chlorite 

Cpx Clinopyroxene 

E Young’s Modulus (GPa) 

E o Seismic Energy (J) 

E s /E p S-wave to P-wave energy ratio 

FAR Fresh Air Raise 

G Shear modulus (geomechanics) 

Ga Billion years 

K Bulk modulus 

Kfs K-Feldspar 

M Moment magnitude 

M o Seismic moment (Nm) 

m N Nuttli Magnitude 

NW Northwest 

OB Orebody 

Opx Orthopyroxene 

Pl Plagioclase 

Qtz Quartz 

RAR Return Air Raise 

R o Source radius (m) 

R a Asperity radius (m) 

SIC Sudbury Igneous Complex 

SRSZ South Range Shear Zone 

SZ Shear zone 

xvi

Chapter 1 

Introduction 

1.1 Background 

The stress system in the mining environment is a result of the superposition of pre-mining and 

mining-induced stresses. When this stress exceeds the strength of the rock mass, failure occurs. 

In the dynamic mine environment, impulsive changes in the stress field caused by blasting or 

more gradual stress perturbations, from excavation for example, can result in failure. The 

excavation process in hard rock mines results in stress concentrations in which strain energy is 

accumulated (Beck et al., 1997). Strain energy in a rock mass can be dissipated by local rock 

fracture or plastic yield, transferred to support, retained as elastic strain, or less favourably, 

radiated as seismic waves emanating from unstable failures such a fault slip, crushing and 

cracking (Beck et al., 1997). 

Seismic monitoring is used to observe this last category of strain release and has become an 

integral part of the mining process. It is of primary importance for the safety of underground 

workers and for uninterrupted mine operation. Monitoring seismicity can also help track the 

physical state of the rock mass over the long term (Alcott et al, 1998; Szwedzicki, 2003; Coulson 

and Bawden, 2008). The onset of seismicity can signal the commencement of rock mass damage 

and yield (Falmagne, 2001) and high event rates and dense event spacing suggest progressive 

damage of the rock mass (Vasak et al., n.d.; Falmagne, 2001). 

Seismicity that is located remote to mining is often attributed to geological structure. Structures 

with high elastic parameters as compared to the host rock are capable of storing more strain 

1

energy (McGarr et al., 1975). Stiff and strong materials such as dykes have been linked to higher 

rates of seismicity (Gay et al, 1984). 

The pre-mining stress tensor can be altered significantly in disturbed ground (Jager and Ryder, 

1999). Rates of seismicity in South African gold mines are noted to be higher when the rock mass 

contains significant structure such as faults, dykes and bedding (Durrheim et al, 2006). Faults can 

provide the large slip surfaces necessary to produce large magnitude events when affected by 

mining activity (Durrheim et al, 2006). Many large events occur in proximity to both faults and 

the advancing excavation face (Gay, 1984). 

There exists a need for a better understanding of the relationship between structure, stress and 

seismicity (Kaiser et al., 2005). This relationship is crucial for seismic hazard assessment and 

mitigation, re-entry protocols, improved mine design, planning of mine geometry, and adequate 

support design. Creighton Mine is used as a study site to explore possible relationships between 

structure and seismicity. 

Creighton Mine, located west of Sudbury, Ontario (Fig. 1.1), is a nickel and copper mine operated 

by Vale Inco. Mining-induced seismicity is a normal part of the mining process at Creighton and 

occurs regularly as the rock mass adjusts to stresses imposed by blasts, development and rock 

extraction. The mine hosts numerous shear zones, making it the ideal candidate for studying the 

relationship between shear zones or local rock anisotropies and seismicity. Large magnitude 

events in the mine are commonly attributed to fault slip without verification. Seismicity related to 

shear zones in Creighton Mine as well as interactions between structures are not well understood. 

Seismicity is frequently linked to geological structure only after large events occur (Kaiser et al., 

2005). 

2

Figure 1.1: Location of Sudbury and Creighton Mine in Ontario and within the Sudbury Basin. 

Creighton Mine experiences increasing seismicity with depth as the mine is being deepened to 

10,000 feet (3048 m; Vale Inco). Events in Creighton Mine are closely monitored by an array of 

uniaxial and triaxial accelerometers to observe trends and prevent injury. Dense clusters of 

microseismic events occur to the south of the 400 Orebody, the main orebody in the lowermost 

levels Creighton Mine, where important infrastructure (ventilation and refuge stations, for 

example) exists. 

To investigate the relationship between structure and seismicity, geological investigations, 

seismological studies and numerical modelling focusing on shear zones were carried out for the 

lower portion of the Creighton Deep, which extends from the 6600 foot level (2012 m, 6600L) to 

the bottom of the mine. Joint characteristics are not considered in this study. For further 

information the reader is referred to Coulson (1996). Studies were conducted for levels on and 

below 7400 feet (2255 m), with emphasis on the 7400 Level (7400L). The results of these studies 

are presented in this thesis. 

3

1.2 Organization of Thesis 

Chapter 2 presents the regional and local geology of Creighton Mine, a brief history of tectonic 

events that affected the Sudbury region, and a summary of regional-scale structural features. The 

geology of the Creighton Deep is described in terms of its rock units and shear zones. Mine-scale 

shear zones are discussed in terms of macroscopic and microscopic features, and kinematics. 

Chapter 3 presents an analysis of mining-induced seismic events at Creighton Mine. Events are 

assessed in terms of spatial and temporal trends and in terms of seismic event parameters. Fault 

plane solutions are generated to explore event mechanisms and assess the relationship between 

faults and seismicity. Lastly, a stress inversion using focal plane solution data is presented and 

compared to regional stresses. 

In Chapter 4 the results of finite and distinct element stress modelling are discussed. Models 

simulate the response of the rock mass to stresses imposed by mining and the influence of the 

Creighton Deep structural system. Results from distinct element models are presented with 

various boundary conditions and geomechanical conditions applied to faults. The general 

response of the rock mass and the influence of faults on stress distribution are discussed. This 

chapter presents a proposed explanation of rock degradation induced by the geometry of the 

excavation. 

Chapter 5 presents a summary of geological work, seismic investigations and stress modelling. 

Seismicity is discussed in terms of a damage process and recommendations for future work are 

offered. 

4

Chapter 2 

Geological Assessment of Creighton Mine 

2.1 Regional Geology of the Sudbury Basin 

The Sudbury Basin (Fig. 2.1), formed at 1.85 Ga by a meteorite impact (Dietz, 1964), is a 27 km x 

60 km elliptical structure located between the southern margin of the Superior Province and the 

northern margin of the Southern Province, approximately eight kilometers northwest of the 

Grenville Deformation Front (Brocoum and Dalziel, 1974). The Superior Province consists of 

Archean granite and gneiss, while the Southern Province comprises metavolcanic and rift margin 

sedimentary rocks including greywacke, greenstone and quartzite. 

Figure 2.1 (A) Location map of Sudbury in Ontario, Canada (B); the location of the Sudbury and 

surrounding tectonic provinces. Modified from Ames et al., 2005. SRSZ = South Range Shear 

Zone. 

5

2.1.1 Evolution of the Sudbury Basin 

The Sudbury Basin has been shaped by numerous tectonic events since the early Paleoproterozoic. 

Events that have affected the Sudbury region are listed in Table 2.1. The Archean hinterland of 

the Superior Province rifted at ca. 2.46 Ga, leading to the establishment of a passive margin at the 

southern edge of the Superior Craton (Mungall and Hanley, 2004). Passive margin rocks 

comprise the Southern Province. In the Sudbury area, Southern Province rocks include 

metasedimentary and metavolcanic rocks of the Huronian Supergroup. 

The proposed 2.40-2.20 Ga Blezardian Orogeny (Stockwell, 1982) may represent the first 

Proterozoic compressional deformation event affecting the Sudbury area. Blezardian deformation 

is thought to be responsible for the development of an early tectonic foliation in Huronian rocks 

and large-wavelength, non-cylindrical thick-skinned folds (Riller et al., 1999). 

The Penokean Orogeny (Van Schmus, 1976) initiated at ca. 1.88 Ga with the oblique collision of 

an island arc system with the Superior Craton (Schulz and Cannon, 2007). Before the bulk of the 

Penokean deformation terminated, the Sudbury region was impacted by a meteorite (Dietz, 1964) 

at 1.85 Ga (Krogh et al, 1984). Impact melting and impact induced-melting formed the Sudbury 

Igneous Complex (SIC), characterized by a differentiated pool of norite, gabbro and granophyre, 

lined by a Sublayer Norite, which hosts the bulk of the basin’s rich ore deposits (Dressler and 

Reimold, 2001; Jones, 2005). 

Post-impact deformation features during the Penokean Orogeny are restricted to the southern 

margin of the Sudbury Basin and include folds, faults and shear zones (Cochrane, 1991), which 

are responsible for offsetting and folding the Sudbury Igneous Complex into a doubly plunging 

synform (Brocoum and Dalziel, 1974; Mungall and Hanley, 2004). The Sudbury Igneous 

Complex is filled by the Whitewater Group, which consists of impact-related rocks such as fall- 

6

ack breccia and sediments later deposited in the Penokean foreland basin (Dressler and Reimold, 

2001; Long, 2004). The impact culminated in the emplacement of rich nickel and copper sulfides 

and platinum group metals. 

Table 2.1: Geological Events in the Sudbury Area 

Event Age Reference 

Grenville Orogeny 1.30-.1.00 Ga Van Breemen and Davidson, 

1988 

Intrusion of olivine-diabase Sudbury 

Dykes 

1.238 Ga Krogh et al, 1987 

Intrusion of hornblende-diabase 

Trap Dykes 

1.4 Ga 

Dressler, 1984 

Cochrane, 1991 

Deposition of Whitewater Group 1.85- 1.7 Ga Hemming et al., 1996 

Intrusion of quartz-diorite aplitic 

dykes (Offset dykes) 

Sudbury Event meteorite impact and 

SIC emplacement 

1.850 Ga Krogh et al, 1984 

1.850 Ga Dietz, 1964 

Krogh et al, 1984 

Penokean Orogeny 1.88-1.83 Ga Van Schmus, 1976 

Schulz and Cannon, 2007 

Intrusion of Nipissing Gabbro dykes 

and sills 

2.22 Ga Corfu and Andrews, 1986 

Blezardian Orogeny 2.40-2.20 Ga Stockwell, 1982 

Riller et. al, 1999 

Deposition of Huronian Supergroup 2.45-2.42 Ga Mungall and Hanley, 2004 

Rifting of Superior Province 2.46 Ga Mungall and Hanley, 2004 

Matachewan Dyke Swarm 2.476 Ga Heaman, 1997 

7

2.1.2 Dykes 

The Sudbury Region has been intruded by many generations of dyke swarms. The earliest of 

these is the Matachewan swarm (2.45 Ga; Heaman, 1997; Rousell et al, 1997), which predates 

rifting of the Archean basement. Quartz-diorite dykes (1.85-1.74 Ga), also known as Offset 

Dykes, are composed of impact-related melt rock and sulphides that fill impact-induced fractures 

oriented radially to the Sudbury Igneous Complex (Grant and Bite, 1984). Such dykes constitute 

important metal resources within the Sudbury Basin. Post-basin dyke intrusions include the ca. 

1.4 Ga (Cochrane, 1991) east-west striking hornblende-diabase swarm, known as Trap Dykes 

(Dressler, 1984), and the northwest striking olivine-diabase Sudbury Dykes (ca. 1.24 Ga; Krogh et 

al, 1987). 

All dykes occur in proximity to or in the Creighton Mine. A quartz-diorite Offset Dyke extends 

from the 800 Level to the 6200 Level where it pinches out (Coulson, 1996). Coulson (1996) also 

notes that below the 6600 Level hornblende-diabase and olivine-diabase dykes do not constitute 

important structural elements. At shallower levels and at surface shearing occurs along dykes, as 

shown in geological mapping (Vale Inco). All dykes are also intersected and offset by late-stage 

faults and fractures (Cochrane, 1991). 

2.1.3 Regional faults 

The Murray Fault system strikes east-northeast and extends 300 km from Sault Ste. Marie to 

Sudbury (Fig. 2.1). Zolnai et al. (1984) propose that the Murray Fault System initiated as 

extensional ductile faults, overprinted by steepening of the faults and brittle thrusting during the 

Penokean Orogeny, and further reactivated as strike-slip during the Grenville Orogeny. The 

8

Murray Fault, the principal fault of the system, shows evidence of right-lateral displacement with 

a total estimated lateral displacement of 1 kilometer (Cochrane, 1991). 

The Creighton Fault, part of the Murray Fault System, extends 48 km from Drury Township, west 

of the Sudbury Basin, east to Coniston where it intersects the Grenville Front (Fig. 2.1; Cochrane, 

1991). It trends east to east-northeast and dips steeply north between 75 and 90 degrees 

(Cochrane, 1991). Previous work by Cochrane (1991) found that the Creighton fault has a net 

slip of 560 metres. The north side is displaced 540 metres eastward and 150 metres downward 

relative to the south side. The Creighton fault truncates offset dykes, olivine-diabase dykes, as 

well as the southern tip of the Creighton embayment, leading Cochrane (1991) to suggest that the 

Creighton Fault is younger than 1.24 Ga. Akin to Zolnai et al. (1984), Rousell et al. (1997) 

propose that the cumulative slip of the Creighton fault reflects an early normal movement during 

the deposition of the Huronian Supergroup, followed by repeated reverse-sense reactivation 

during the Penokean Orogeny, and dextral-oblique faulting in the Neoproterozoic. 

The Creighton Fault diverges from the Creighton embayment at depth. Because the fault dips 

more steeply than the embayment, which dips at 60 degrees, the Creighton Fault does not intersect 

mine excavations. A splay between Murray and Creighton Faults, termed the Murray-Creighton 

Splay bounds the eastern margin of the Creighton Embayment and is intersected on levels above 

the Creighton Deep as the 118 Shear Zone (Hodder, 2002). Parallel features to both the Creighton 

Fault and Murray Creighton Splay fault are reflected in structures within the Creighton Deep 

(Tulk, 2001; Hodder, 2002). 

The Creighton Fault was observed at surface along HWY 144, west of Creighton Mine (Fig. 2.2). 

Rock in proximity to the Creighton fault is jointed and veined. Brittle jogs in rock in proximity to 

the fault and offset veins and dykes confirm a dextral sense of motion (Fig. 2.3). 

9

Figure 2.2: Local geology map modified from Ames et al. (2005). Corresponding sections are represented 

by Figure 2.4A and B. 

Figure 2.3: Horizontal view of a fault jog in proximity to Creighton Fault. The fault was observed at 

surface, west of Creighton Mine along highway 144, as shown by the black dot in Figure 2.2. Card used for 

scale is 9 cm in length. 

10

2.2 Local Geology of Creighton Mine 

Creighton Mine is located approximately 18 km SW of downtown Sudbury. It is situated on the 

southern rim of the Sudbury Igneous Complex in an embayment of sublayer norite, called the 

Creighton Embayment (Fig. 2.2). 

Fieldwork conducted in summer 2008 at Creighton Mine targeted shears zones exposed 

underground as well as faults exposed at the surface surrounding the mine. The underground 

study was concentrated between 6600 feet (2012 m) and 7940 feet (2420 m) deep, coinciding with 

the 6600 Level (6600L) and the 7940 ramp at the base of the mine. This portion of the mine is 

known as the Creighton Deep. Emphasis was placed on levels below 7400 feet (2256 m). 

Development is ongoing as the mine strives to reach a depth of 10,000 feet (3048 m; Vale Inco), 

as shown in Figure 2.4. In the study area the 400-Orebody is the main mining target (Fig. 2.4A, 

2.4B). Above 6600L the orebody follows the footwall-hangingwall contact, which is defined by 

the limits of the embayment. In the lowermost levels, the main orebody diverges from the 

footwall-hangingwall contact such that it is nearly encased in the footwall (Fig. 2.4A). 

Footwall rocks surrounding the embayment (Fig. 2.2; 2.4A) consist of the Creighton Pluton 

granite and metavolcanics of the Elsie Mountain Formation (Ames et al., 2005). Granitic footwall 

units are medium-grained to coarse-grained, having variable alkali feldspar content and are 

massive to weakly foliated. Main mineral constituents include alkali feldspar (50%), often with 

alteration to sericite, quartz (40%) and biotite (10%). 

Metagabbro is massive and fine to medium-grained (1 mm). It consists primarily of chlorite and 

biotite (80%) with quartz (5-10%), plagioclase feldspar (5-10%) and minor amounts (5%) of 

11

opaque minerals and other mineral constituents. Specimens from high-strain areas exhibit a fabric 

expressed as preferential alignment of biotite and/or chlorite. 

Other rock units found interspersed in footwall rocks include alkali feldspar granite porphyry 

(locally termed black porphyry) and Sudbury breccia. The black porphyry has a matrix composed 

of biotite and chlorite and has quartzo-feldspathic porphyroclasts. This unit is locally strained; 

metre-wide strain localizations are expressed as elongated porphyroclasts in the vertical plane. 

Figure 2.4A: Vertical cross-section of Creighton Mine showing geometry of footwall and hangingwall 

rocks as well as orebodies. Approximate section line is shown in Figure 2.2. Level numbers correspond to 

depth in feet; depth in metres is shown at the far right. Study area is shown between two dashed lines. 

Plum Orebody is referred to 6100 in this diagram. No vertical exaggeration. Figure modified from Vale 

Inco composite section, Creighton Mine. 

12

B West East B’ 

Figure 2.4B: Longitudinal section of Creighton Mine showing idealized geometry orebodies. 

Approximate section line is shown in Figure 2.2. Level numbers correspond to depth in feet. Plum 

Orebody is referred to 6100 in this diagram. No vertical exaggeration. Figure modified from Vale Inco 

idealized longitudinal section for Creighton Mine. 

13

Sudbury breccia occurs as sub-rounded clasts of footwall units of variable size, contained in a 

dark matrix. 

Norite is found in the hanging wall within the embayment and is the basal unit of the Sudbury 

Igneous Complex. The norite unit is massive and medium-grained (up to 4 mm) and contains 

euhedral to subhedral grains of biotite and orthopyroxene with chlorite alteration, hosted in a 

matrix of plagioclase. 

2.3 Mine-Scale Faults 

The Creighton Deep contains four families of faults: south-west striking shear zones of the 118 

Shear System, Footwall family shear zones, east-west-striking shear zones and splays between 

faults of the 118 Shear System (Table 2.2, Fig. 2.5). All orientations, except where stated, are 

expressed in ‘8-Shaft’ coordinates in which grid north is subject to a 25-degree clockwise rotation 

from geographic north. 

Shear zones are typically schistose with biotite mineral lineations. Composite foliation planes and 

mylonite textures are also common but difficult to discern in underground conditions. Quartz 

veins with minor calcite are frequently associated with shear zones in the Creighton Deep. Shear 

zones dissect all rock types and can be found within rock units, at the contact between two 

lithological units, at ore-rock contacts or along dykes. Within granitic units, shear zones are 

biotite-rich, strongly foliated and often display near-vertical biotite mineral lineation in the 

foliation plane, whereas they are more chlorite-rich within metagabbro. Shear zones of the 118 

Shear System have a consistent inter-shear spacing of approximately 200 feet, as shown in Figure 

2.5. 

14

Table 2.2: Fault systems within the Creighton Deep 

System Orientation Shear Zones 

118 Strikes SW between 230°-260° 

Dips NW between 75°-85° 

Footwall Strikes NW ~313°, 

Dips NE 55° 

Northwest 

Return Air Raise 

402 Shear 

Plum Shear 

Fresh Air Raise Shear 

Fresh Air Raise-Type Shear 

Footwall Shear 

Footwall-Type Shear 

EW 

Splays 

East-west striking with opposite 

dips between 70° and 80° 

Steeply-dipping 

Link SW-striking shears 

1290 Shear 

400-East Shear 

Grizzly Splay 

461 Splay 

Figure 2.5: Level plan for the 7400 Level in the Creighton Deep showing excavated drifts and sills, shear 

zones and approximate shape of the 400 Orebody. Map modified from Vale Inco 7400 Level Plan. NW = 

Northwest; RAR = Return Air Raise; FAR = Fresh Air Raise. The 400-East Shear Zone is found on the 

7810 Level. 

15

Thin sections were made from collected oriented specimens. These were cut parallel to lineation 

and perpendicular to foliation as well as perpendicular to both lineation and foliation. Thin 

sections were examined for fabrics and microstructures. 

Shear zone kinematics are of economic interest as many of the shear zones in Creighton Mine 

control the shape and distribution of orebodies. Shear-sense indicators in this thesis are of interest 

for establishing the tectonic heredity of the shear zones in the Creighton Deep. Microstructural 

analysis is used to characterize faults and deformation mechanisms. A summary of faults and 

fault characteristics is presented in Table 2.3. 

For consistency with current mapping and because its strike, dip and shear zone spacing are 

conformable to other shear zones observed within the 118 System within the study area, the Plum 

Shear Zone is assigned to the 118 Shear System. The Plum Shear Zone is described as its own 

shear system by Seidler (2008) because of its association with the Plum Orebody (referred to as 

6100 Orebody in Fig. 2.4A and 2.4B). In previous structural work by Tulk, (2001) the Plum 

Shear Zone is described as a prominent NNE-striking splay fault. 

Shear zones have been mapped by Vale Inco staff as planar and continuous features, though shear 

zones can vary in attitude and thickness and are not always continuous in their extent. The 1290 

and Footwall Shear Zones seem to be continuous features while 118 System shear zones and 

splays cannot always be traced level-to-level. 

16

Table 2.3: Summary of Fault Characteristics 

Shear Name 

Approximate 

Strike/Dip 

Rock Type 

Features 

Footwall Shear 

Zone 

N 313/55° NE Biotite/chlorite schist • 0.3-0.6 m width 

• Strongly developed schistosity 

• Sub-vertical mineral lineations, 

• Near horizontal crenulation 

• C-S-C’ fabrics 

• Associated damage to shotcrete 

• Predominant reverse sense-of-shear 

1290 Shear Zone N 270/80° N Biotite schist with 

concordant quartz veins 

• Greater than 6 m 


• Biotite mineral lineation 

• Abundant concordant veins 

• Unknown sense-of-shear, reported strike-slip offset 

400-East Shear 

Zone 

Grizzly Shear 

Zone (splay) 

Northwest Shear 

Zone 

Return Air Raise 

Shear Zone 

N 090/70° S Biotite-rich phyllonite • Weak schistosity 

• Sub-vertical biotite mineral lineation 

• Quartz-carbonate veins 

• Sub-horizontal slickenlines 

• Strike-slip overprinting 

N 053/75° WNW Biotite schist • 0.5 m width 

• Sharp contact with host rock 


• Biotite mineral lineation 

• Near-horizontal crenulation 

• Apparent reverse sense-of-shear 

N 247/75° NW Biotite schist (VI)* • 3 m in width 

• Strongly developed schistosity (VI) 

• Limited exposure and exposure restricted by 

shotcrete 

• Unknown Sense of Shear 

N 244/85° NW Ultramylonite • Strongly developed foliation, 

• Sharp contacts with ore/host rock 

• Associated damage to shotcrete 

• Unknown Sense of Shear 

402 Shear Zone N 241/85° NW Biotite schist (VI) • 1.2 m in width 

• Strongly developed schistosity (VI) 

• Exposure restricted by shotcrete 

• Reverse sense-of-shear (Siddorn, 2006) 

Plum Shear Zone N 235/80° NW Biotite schist (VI) • 3 m in width (variable) 


• Concordant quartz-carbonate veins (VI) 

• Unknown sense-of-shear 

Fresh Air Raise 

Shear Zone 

N 258/80° NW 

Mylonite/ 

ultramylonite 

• 1.5 m in width (7400L) 

• Strong/weak schistosity (location dependent) 

• Apparent reverse sense-of-shear 

Fresh Air Raisetype 

Shear Zone 

N 249/80° NW Quartz-metagabbro • Well-foliated, defined by quartz and biotite. 

• Weak mineral alignment; No mineral lineation 

• Foliation-parallel quartz veins 

• Unknown sense-of-shear 

*(VI) indicates information gathered from Vale Inco digital geological maps 

17

2.3.1 Footwall Shear Zone 

The Footwall Shear Zone strikes northwest (N313°) and dips to the northeast, with an average dip 

of 55° (Fig. 2.5). It is recognized on all levels in the study area as a strongly developed, biotite 

and/or chlorite-rich schistose zone of localized deformation (Fig. 2.6A, B). The shear measures 

0.3 m - 0.6 m wide, often with ~1 m damage zones to either side that are defined by shear-parallel, 

closely spaced joints and localized damage to mine-support, including breaking of wire mesh and 

cracking and failure of shotcrete (Fig. 2.6A). Near-vertical biotite mineral lineations are often 

visible on foliation planes. The Footwall Shear Zone is not an ore-controlling shear, but dissects 

footwall and hangingwall rocks. 

In thin section the Footwall Shear has a variable composition. It is often composed of 

predominantly quartz and biotite with plagioclase, microcline, chlorite and minor sericite, calcite, 

opaque minerals and minor amounts of other mineral constituents; however in some locations, it is 

almost wholly composed of chlorite. The variable composition of the Footwall Shear is thought to 

reflect the lithological differences of the host rock. 

In samples with abundant quartz, quartz grains have a bimodal grain size distribution (Fig. 2.6C): 

larger grains are found in quartz ribbons with sub-grain boundaries and smaller grains are found in 

shear bands. The quartz ribbons and preferential alignment of biotite creates a discontinuous 

fabric. In some samples, biotite forms an anastomosing fabric with C, S and C’ planes, 

compatible with top-to-the-SW shear sense (Fig. 2.6D). 

18

Figure 2.6: (A) Damage to shotcrete and mesh along the Footwall Shear Zone; (B) localized shearing along 

the Footwall Shear Zone; (C) Quartz ribbons; (D) S-C’ fabrics in thin section; (E) Shear-sense indicator in 

thin section. Minerals shown in white are quartz. Bt, Biotite; Chl, Chlorite’ Kfs, K feldspar; Qtz, Quartz. 

Where observed underground, an apparent reverse-sense, top-to the-southwest component of 

motion is inferred from the development of C’ shear bands. In thin section, C-S fabrics formed by 

19

iotite grains, fish structures and rotated clasts (Fig. 2.6D, E) indicate a dominant reverse 

component of shear with a possible dextral component. Fewer shear-sense indicators and fabric 

alignment in thin sections cut perpendicular to lineation suggest that the major shear component 

occurred in the direction of lineation. This supports Tulk’s (2001) suggestion of reverse-sense 

motion on the Footwall Shear Zone. Apparent offset of the 1290 Shear Zone by the Footwall 

Shear Zone supports a dextral component of motion and suggests that the Footwall Shear Zone is 

younger than the 1290 Shear Zone. 

Shears with similar orientations to the Footwall Shear Zone have been inferred from ore shapes 

below 8000 feet depth (Seidler, 2008), suggesting that the Footwall Shear Zone may be part of a 

system of parallel shear zones. 

2.3.2 1290 Shear Zone 

The 1290 Shear Zone strikes east-west and dips steeply 80° to the north (Fig. 2.5). It is observed 

on the 6400 Level (Fig. 2.7A, B) and in the back (ceiling of the drift) on the 7810 Level but has 

been mapped as shallow as the 5600 Level. Its width is reported to be greater than 6 m wide 

(Seidler, 2008) and is characterized by a strongly developed biotite-rich schistosity, near-vertical 

biotite mineral lineation and abundant quartz-carbonate (quartz with minor calcite) veins, oriented 

parallel to the foliated schist. The 1290 Shear Zone is ore-controlling and is associated with the 

1290 Orebody. 

In thin section, the 1290 Shear Zone is composed of biotite, quartz, K-feldspar and calcite (Fig. 

2.7C). The preferential alignment of biotite defines a strong fabric. Grain-size reduction is 

observed in quartz shear bands and larger elongate calcite grains align with the shear fabric (Fig. 

2.7C). Larger grains are formed by multi-granular K-feldspar. 

20

Figure 2.7: (A) The 1290 Shear Zone fabric; (B) 1290 Shear Zone on the 6400 Level; and (C) biotite, 

quartz and calcite fabric of the 1290 shear zone in thin section, from the 6400 Level. Bt, biotite; Cal, 

Calcite; Qtz, Quartz. 

No clear shear-sense indicators are observed. Galkin and Mungall (1995) report that the 1290 

Shear Zone has a dextral sense and as such could be related to late dextral-sense movement along 

Creighton Fault System (Rousell et al., 1997; Cochrane, 1991). 

21

The orientation of the 1290 Shear is parallel to that of the Creighton Fault but is offset by the 

Footwall Shear Zone (Seidler, 2008). This implies that the 1290 Shear Zone predates the last 

episode of movement along the Footwall Shear Zone. 

2.3.3 400-East Shear Zone 

The 400-East Shear Zone (Fig. 2.8A, B) is observed on the 7810 Level only. The 7810 Level plan 

can be found in Appendix A (Fig. A6). This shear zone strikes east-west and dips to the south at 

approximately 70°. The width of this shear zone and its associated damage zone is not defined 

due to the proximity of the 1290 Shear Zone and the drift boundaries. The shear zone is composed 

of biotite-rich phyllonite with sub-vertical biotite mineral lineations and minor quartz veining. 

Lineations along a number of shear-parallel, persistent fractures are overprinted by near-horizontal 

slickenlines. The 400-East Shear is ore-controlling and is associated with the 400-East Orebody 

(Fig. 2.4). 

In thin section, the 400-East Shear Zone consists mainly of quartz with lesser amounts of biotite, 

microcline, plagioclase and calcite (Fig. 2.8C). Light coloured minerals have variable grain size 

distributions with biotite composing a discontinuous fabric. Biotite anastomoses around larger 

grains of quartz and feldspar and sometimes outlines multi-granular fish-type structures. 

Extensional cracks are filled with calcite and fibrous quartz (Fig. 2.8C, D). Calcite twins are bent 

(Fig. 2.8B). 

A drag fold (Fig. 2.8A) along a shear-parallel fracture in the face of the 6646 Sill suggests a 

normal top-to-the-south component of motion. Slickenlines along fractures indicate a more recent 

lateral component of movement, which postdates ductile shearing. 

22

Figure 2.8: Images of (A) the 400-East Shear showing a normal-sense drag fold; (B) schematic diagram of 

fold in A on the curving transition from the face to the back (top) of the drift, (C) shear zone fabric 

including a calcite vein; and (D) horizontal view of deformed calcite crystals in thin section. Bt, biotite; 

Cal, calcite; Qtz, quartz. 

2.3.4 Northwest Shear Zone 

The Northwest Shear Zone strikes N247° and dips 75° to the NW (Fig. 2.5). Access to this shear 

zone is restricted due to extensive shotcrete. The shear zone is not visible in its projected location 

23

on the 7680 Level but parallel features are mapped, including a tectonic foliation and veining. 

The shear zone is described in Vale Inco mapping as strongly biotitic and up to 3 m wide. This 

shear is not ore controlling and is parallel other shears in the 118 Shear System and to the Murray- 

Creighton Splay fault. 

2.3.5 Return Air Raise Shear Zone 

The Return Air Raise Shear Zone is observed on Levels 7400, 7530 and 7680. The shear zone 

strikes N244° and dips 85° to the NW (Fig. 2.5). On the 7400 Level, The Return Air Raise Shear 

Zone occurs as a series of closely set, parallel, brittle joints in a zone 40 cm wide. The shear zone 

is divided at the base of the drift and straddles massive sulphides. One strand of the shear zone is 

expressed as a 5 cm wide ultramylonite zone that forms a more cohesive and sharp boundary with 

both ore and footwall rocks. Wall rock within a few metres of the shear zone is brecciated and 

hosts a stockwork of carbonate veins. Although rock exposure is covered on the 7530 Level, the 

shotcrete (Fig. 2.9A) and concrete pad (Fig. 2.9B) is damaged by cracks that align with the strike 

of the Return Air Raise Shear Zone. 

In thin section, the Return Air Raise Shear Zone contains variably-sized biotite, chlorite, lesser 

amounts of quartz and minor amounts of plagioclase, some with sericite alteration. In some 

locations minor amphibole and calcite occur. The strong foliation is defined by preferentially 

oriented quartz and chlorite (Fig. 2.9C, D). Calcite pressure shadows occur on larger amphibole 

grains. Quartz ribbons with sub-grain boundaries are also oriented along foliation, which is 

defined by elongate biotite and chlorite. Quartz grains contain many sub-grain boundaries. 

No sense-of-shear was ascertained from hand sample or thin section, nor is a sense-of-shear for 

this shear zone reported in previous studies. 

24

Figure 2.9: (A) Photograph of the cracked concrete pad floor along the Return Air Raise Shear Zone on 

7530L; tip of boots for scale; (B) cracked shotcrete on wall of 7530L, same location as A; (C) thin section 

of shear zone fabric on 7680L; (D) thin section of shear zone fabric on the 7400 Level. Bt, biotite; Cal, 

calcite; Chl, chlorite; Qtz, Quartz. 

25

2.3.6 402 Shear Zone 

The 402 Shear Zone strikes N241° and dips 85° to the NW (Fig. 2.5). Access to this shear zone is 

restricted due to extensive shotcrete with no visible damage and the shear zone is not well mapped 

below the 7400 Level. The shear zone reportedly has a strong biotite-rich schistosity and 

measures approximately 1.2 m in width (Vale Inco). This shear zone is parallel to the regional 

Murray-Creighton Splay Fault and thus belongs to the 118 System. 

2.3.7 Plum Shear Zone 

The Plum Shear Zone strikes N235° and dips 80° NW (Fig. 2.5). Access to this shear zone is 

restricted due to extensive shotcrete and enhanced support. No damage to shotcrete was observed. 

This shear zone is reported to be 3 m in width, widening in the Creighton Deep, and has a strong 

biotite schistosity and concordant quartz-carbonate veining (Vale Inco). Previous mapping 

suggests that the shape of the 461 orebody reflects the presence of the Plum Shear (Vale Inco). 

Nearby faults were observed to have clear reverse-sense kinematics as shown by quartz sigmaporphyroclasts 

within minor biotitic shear zones (Fig. 2.10 A, B) as well as the development of a 

foliation in the granite that rotates into the plane of shear (Fig. 2.10 C, D). Normal-sense brittle 

overprinting along shear planes is shown by the displacement of granitic dykes (Fig. 2.10E-H). 

26

Figure 2.10 (A) Shear foliation, indicating reverse ductile movement; (B) Sketch of fabric in A. Dashed 

lines show foliation; (C) quartz sigma porphyroclasts showing ductile reverse-sense movement; and (D) 

Sketch of sigma porphyroclasts; (E) Rock face with brittle fractures and offset granitic dykes; (F) sketch of 

displaced dyke (G) foliation showing a reverse, ductile sense-of-shear overprinted by brittle normal-sense 

movement marked by an offset granite dyke; (H) sketch of overprinting relationships in G. Offset is marked 

by displaced dyke. Dashed lines indicate foliation. 

27

2.3.8 Fresh Air Raise Shear Zone 

The Fresh Air Raise Shear Zone strikes N258° and dips 80° to the NW (Fig. 2.5) and is parallel to 

the orientation of the Murray-Creighton Splay fault. It is observed on 7400 and 7200 Levels with 

variable grain size and texture. The shear zone on 7200 Level is hosted in cohesive, highly 

strained granite and exhibits a well-defined quartz and biotite foliation. Some quartz-rich veins 

oriented parallel to the shear zone are present in this location. 

On the 7400 Level, the Fresh Air Raise Shear Zone is expressed as a 1.5 m wide zone of 

ultramylonite with a fine-grained biotite-rich fabric. The shear zone contains deformed inclusions 

of granitic material and is hosted in strained porphyritic alkali feldspar granite. The Fresh Air 

Raise Shear Zone in this location is associated with localized damage to wire mesh. 

In thin section the Fresh Air Raise Shear Zone is composed of bimodal-sized microcline, quartz 

and biotite and contains minor calcite and sericite (Fig. 2.11A-D). Chlorite is present in the 

ultramylonite specimen in addition to these minerals. Biotite forms discrete bands that 

anastomose around coarse K-feldspar grains. K-feldspar shows reduction in grain size in finegrained 

bands. Ribbons of anhedral quartz also anastomose around the coarser grains. Calcite is 

found in strain shadows adjacent to multi-granular K-feldspar clasts (Fig. 2.11A) and as subhedral 

grains that are elongated along foliation. 

In the ultramylonitic sample (Fig. 2.11B-D) there is a distinct reduction in grain size, a welldeveloped 

foliation, quartz ribbons and rotation of angular clasts (Fig 2.11C, D). Shear-sense 

indicators (eg. Fig. A) suggest a possible reverse component of motion. 

28

Figure 2.11: Thin sections of the Fresh Air Raise Shear Zone showing (A) Shear and C’ planes; (B) 

ultramylonite textures; (C) Detail of thin section in (B); and (D) detail of thin section in (B). Bt, biotite; 

Cal, calcite; Chl, chlorite; Cpx, clinopyroxene; Opx, orthopyroxene; Qtz, quartz. 

2.3.9 Fresh Air Raise-type Shear Zone 

The Fresh Air Raise-Type Shear Zone is observed at the lowermost point of the mine on the 7940 

ramp. The shear zone strikes N249° and dips 80° to the NW and persists beyond the width of the 

drift and may extend to the Fresh Air Raise Shear Zone (Fig. 2.5). This shear zone displays a 

29

strong foliation defined by biotite and quartz. Quartz-rich veins are oriented parallel to the 

foliation plane. 

Shear fractures overprint the shear zone at a high angle to the foliation as evidenced by quartz-rich 

veins. Such veins mark several cm-scale reverse shear-sense displacements along fractures, 

though no slickenlines were observed (Fig. 2.12A). 

Figure 2.12: Images of the Fresh Air Raise-Type Shear (A) in situ on the 7940 ft. ramp and (B) in thin 

section. Bt, biotite; Chl, chlorite, Kfs, K feldspar. 

In thin section, the Fresh Air Raise-type Shear Zone contains a high proportion of quartz, biotite 

and microcline and a lesser amount of plagioclase, chlorite, amphibole and opaque minerals. 

Biotite grains show a preferential alignment and create an intermittent fabric within the specimen 

30

(Fig. 2.12B). Reduction of quartz grain size occurs in shear bands. Within the Fresh Air Raisetype 

Shear Zone there is evidence of high strain but little evidence of shearing, though this has 

been named a shear zone by mine staff. As a result, sense-of-shear was not determined for the 

Fresh Air Raise-Type Shear Zone. 

2.3.10 Splays and Minor Shear Zones 

The best-exposed splay fault between shears of the 118-System is the Grizzly Shear Zone, 

exposed on the 7400 Level (Fig. 2.5). It is a minor shear zone, adjacent to mapped splays and 

links the Plum Shear Zone and Fresh Air Raise Shear Zone. The Grizzly Shear Zone strikes 

northeast, dips steeply 75° to the southeast and measures approximately 50 cm in width. It has a 

well-developed biotite schistosity with biotite mineral lineations that trend to the southwest and 

plunge approximately 55°. Near-horizontal crenulations deform the shear zone foliation. The 

Grizzly Shear Zone forms a sharp contact with its hosting granite and contains boudinaged wall 

rock. 

The shear zone is cohesive but a 2-3 mm aperture occurs at the easternmost schist-granite 

boundary. This extension may not necessarily represent tectonic extension but rather unclamping 

of the confining rock due to the close proximity of the shear zone to an excavation (a drift). 

In thin section the Grizzly Shear Zone contains biotite, chlorite and plagioclase with minor 

amounts of quartz, calcite and K-feldspar. The shear zone fabric is defined by biotite that weaves 

around larger plagioclase grains (Fig. 2.13A). Chlorite found within the Grizzly Shear Zone does 

not contribute to the specimen fabric. 

Reverse-sense top-to-the-northwest displacement is interpreted from sheared granite boudins (Fig. 

2.13B, C), as well as offset granite veins. 

31

Figure 2.13 (A) The Grizzly Splay shown in thin section. Bt, biotite; Chl, chlorite; Pl, plagioclase; (B) The 

Grizzly Splay as observed on the 7400 Level. Shearing of granitic boudins indicates reverse-sense 

displacement; (C) sketch of boudins within the Grizzly Splay. 

The 461 Shear Zone is another splay fault and links the 402 Shear Zone and the Return Air Raise 

Shear Zone (Fig. 2.5). This splay is no longer visible due to limited access and shotcrete, but has 

been previously mapped as a 0.6 – 1.2 m wide zone of well-developed biotite-rich schistosity 

(Vale Inco). The shear zone is ore-controlling and hosts the 461 Orebody. Minor shear zones in 

the vicinity of the 461 Shear are described as having reverse sense-of-shear (Siddorn, 2006). 

Minor centimetre-scale shear zones occur parallel to the 118-Shear System and at locations of 

competency contrasts such as lithological contacts or along dyke margins. 

32

2.3.11 Late-Stage Fractures 

The youngest features in Creighton Mine are late-stage fractures (Cochrane, 1991). These 

fractures crosscut steeper-dipping foliation and fault fabrics, postdating shear zone formation. 

Subhorizontal shear fractures (apparent orientation in face) and fractures filled with quartzcarbonate 

material show evidence of small centimetre-scale displacement. Slickenlines are 

observed along fractures found between the 402 and Return Air Raise Shear Zones on the 7810 

Level, though direction of motion cannot be discerned. Reverse offset was noted along filled 

fractures in this location (Fig. 2.14A, B). Displacement along shallow fractures, such as those 

shown in Figures 2.14C and D, are observed in many locations throughout the mine. Sense of 

displacement can not always be discerned (Fig. 2.14D). 

Figure 2.14: Shallow shear fractures in Creighton Deep. (A) Secondary fractures and displacement occur 

oblique to shear zone foliation; (B) oblique relationships are shown in sketch of photograph in A; (C) 

shallow-dipping fractures truncate veins; (D) feature orientations are depicted in a sketch of photograph in 

C. Direction of displacement is unknown. 

33

2.4 Discussion: Fault Reactivation 

Identifying shear zone paleokinematics is of great importance to understanding ore distribution for 

mine planning and establishing tectonic heredity and fault character; neokinematic relationships, 

however, are of importance for studying mining-induced fault reactivation and seismicity. 

Significant differences in the behaviour of the shear zones in the Creighton Deep at the time of 

their formation and in their present state are discussed in this section. 

2.4.1 Geometric and kinematic summary 

Faults in Creighton Mine were formed as ductile shear zones. This is demonstrated by the 

development of a strong foliation, mylonite and ultramylonite textures, mineral elongation 

lineations and rotation of inclusions. The Footwall Shear Zone, shear zones of the 118 System 

and splays between the 118 System shear zones have ductile, reverse-sense component of shear 

(Fig 2.15). 

Figure 2.15: Block model depicting geometry and paleokinematics of mine-scale faults in the Creighton 

Deep, with respect to grid-north and possible paleo-reactivation sense of faults. 

Seismogenic mining-induced reactivation of shear zones occurs as brittle failures, releasing 

energy through the breaking of asperities and frictional sliding (Scholz, 2002: p. 43-52). 

Examination of microstructures shows that shear zones are healed with little evidence of brittle 

34

overprinting (Cochrane, 1991; Coulson 1996). Observed examples of brittle reactivation within 

the shear zones include: 

 

Horizontal slickensides along the 400-East Shear Zone. These indicate lateral movement, 

overprinting previous vertical displacement. 

 

Brittle fracturing of shotcrete along the strike of the Return Air Raise (2.9A, B) and 

Footwall Shear Zones. 

 

Extension in proximity to the Grizzly Shear Zone. This is likely the result of unloading 

induced by excavation of a nearby drift. 

 

Normal-sense movement along fractures in proximity to the Plum Shear Zone, as 

indicated by displaced dykes and slickensides along the fracture surface (2.10A-H). This 

overprints previous ductile, reverse-sense motion along the fracture as indicated by rock 

shear-sense indicators. 

 

Late-stage brittle fractures that intersect and displace shear zones (Fig 2.14). Offset 

fractures are observed in the Fresh Air Raise-type Shear Zone (Fig. 2.12B). 

The geometry of brittle features is incompatible within a single stress regime, requiring a change 

in far-field stresses to have occurred. Previous work by Cochrane (1991) on levels above the 

Creighton Deep indicates that late-stage faults in Creighton Mine have strike-slip displacement, 

overprinting earlier reverse-sense displacement that is recorded by ductile features within the 

shear zones. This is supported by near-horizontal slickenlines along late-stage features, similar to 

those are observed along the 400-East Shear Zone. Sense-of-shear along late-stage faults was not 

determined by Cochrane (1991). 

35

2.4.2 Evolving Stress System in the Sudbury Basin 

The geometry and kinematics of the shear zones in the Creighton Deep are not compatible with 

either the Andersonian (Anderson, 1951) or Riedel faulting model (Freund, 1974), particularly the 

reverse sense along the NW-trending Footwall Shear Zone. 

Fault geometry and kinematics 

within Creighton Mine are best explained by an evolving stress system. Table 2.4 summarizes 

tectonic events that have affected the Sudbury Basin. 

Changes in the stress tensor are recorded in the tectonic history of regional-scale faults. The 

Creighton Fault was formed as a normal fault and was reactivated as a reverse fault during the 

Penokean Orogeny and subsequently reactivated as a strike-slip fault in the Neoproterozoic 

(Zolnai et al., 1984; Rousell et al., 1997; Table 2.4). Such changes along regional-scale faults 

may provide insight into the faulting history of mine-scale shear zones in the Creighton Deep, as 

shown in Table 2.4, though ages for mine-scale shear zones in Creighton Mine are unknown. An 

age of 1.7-1.6 Ga was determined by Bailey et al. (2004) for steeply-dipping reverse-sense shear 

zones in the Thayer Lindsley mine, also located on the southern rim of the Sudbury Igneous 

Complex. Similar to shear zones in the Creighton Deep, the Thayer Lindsley shear zones are 

steeply-dipping, strongly-foliated, and biotite-rich and have mineral lineations with steep rakes. 

The Thayer Lindsley shear zones are associated with the South Range Shear Zone (Fig. 2.1), 

whose formation has been linked to the Mazatzal and Labradorian Orogenies (Bailey et al., 2004) 

and Penokean Orogeny (Shanks and Schwerdtner 1991). 

36

Table 2.4: Summary of Proterozoic tectonic events, modified from Rousell et al., 1997 

37

The 1290 Shear Zone and the 118 System shear zones were fit to a Riedel model in previous work 

based on ductile shear-sense indicators observed in the Creighton Deep (Siddorn, 2006; Fig. 2.16). 

Figure 2.16: Riedel Model of 1290 and 118-System shear zones, modified from Siddorn (2006). 

In this model, shortening along shear zones of the 118 Shear System and lateral motion along the 

1290 Shear Zone are accounted for by NW-SE directed compression. This is compatible with the 

maximum principal stress direction and regional fault style during the Penokean Orogeny and 

during the formation of the South Range Shear Zone (Fig. 2.17). 

Figure 2.17: NW-SE Penokean compression, possibly responsible for forming 1290 and 118 System 

shear zones, as shown in the top left Riedel model. 

Oblique-reverse motion along the Footwall Shear does not fit the Riedel configuration, suggesting 

multiple periods of fault activity. The apparent offset 1290 Shear Zone by the Footwall Shear 

Zone further supports this. Late-stage lateral-sense motion along steeply-dipping faults is 

compatible with a maximum principal stress direction oriented NNW-SSE (Cochrane, 1991). 

38

Both of these inferred stress directions differ from the current stress tensor in which the maximum 

principal stress is oriented E-W and the minimal principal stress is near-vertical (Cochrane, 1991; 

Coulson, 1996; Malek et al., 2008). According to Anderson (1951), this configuration of 

maximum principal stresses should produce reverse faults. In the absence of high pore fluid 

pressure, it is unlikely that the steeply-dipping SW-striking shear zones in Creighton Mine could 

be reactivated in a reverse sense (Sibson, 1988). 

The medium and intermediate stresses at Creighton Mine are similar in magnitude (Coulson, 

1996). Inversion of the intermediate and minimum stresses would favor strike slip failure, which 

is possible if faults are in a state of critical stability, as proposed by McKinnon (2006). Mininginduced 

perturbations to the regional stress tensor are likely to produce either extensional failures 

via reduction of normal force on shear zones (unclamping) incurred by rock extraction or stressinduced 

strike-slip faulting. Failure mechanisms are explored through microseismic analysis 

presented in the Chapter 3. 

39

Chapter 3 

Mining-induced Seismicity 

3.1 Creighton Mine Seismic Monitoring Systems 

Seismic monitoring offers the best insight into current rock mass damage processes and failure 

related to mining-induced fault reactivation. Brittle failures can be recorded in real-time as 

seismic events. These can be located within an array of sensors, and source parameters can be 

calculated for each event. 

The Creighton Mine currently experiences high rates of seismicity, averaging over 70 events per 

day. Two seismic systems are in operation at Creighton Mine to detect these events: The 

Engineering Seismology Group (ESG) Hyperion Microseismic System (HMS), and a strong 

motion Hyperion Digital Drum Recorder (HDDR) system. 

The microseismic system consists of 88 channels occupied by 10 triaxial accelerometers 

(consuming 3 channels each) and 49 uniaxial accelerometers, leaving 9 channels free for 

expansion. The HMS sensors are distributed mine-wide. The system records full waveforms, 

allowing for the calculation of the hypocenter location, magnitude and other source parameters. 

The HDDR system is a strong motion system and consists of one geophone on the earth surface. 

This system is reserved for the detection of larger magnitude events, above 0 m N on the Nuttli 

Scale used by the Geological Survey of Canada, which saturate the microseismic system. The 

HDDR system is used to obtain a magnitude for such events. Three triaxial geophones on surface 

40

are, at this time, in the process of being calibrated with the HDDR, which will allow for source 

parameters to be calculated for each macroseismic event in the future. 

3.2 Event Characterization and Classification 

Seismic events can be simply described in terms of location, time of occurrence and magnitude. 

The events can be classified as microseismic events, macroseismic events or blasts. Microseismic 

events have magnitudes less than 0 m N . Macroseismic events have magnitudes greater than 0 m N . 

Such events are either large seismic events or rockbursts that are detected by the HDDR system. 

Mining-induced events (microseismic and macroseismic) can be further classified by their 

triggering mechanisms. Within the study area, two types of microseismic events are observed. 1) 

Blast-induced events can be categorized as development or production-related events. Events 

related to development cluster around drifts and progress in time and space with the development 

of mine infrastructure (Fig. 3.1A). Events related to production are more energetic and cluster 

spatially and temporally around blast sites (Fig. 3.1B). Blast-induced events occur immediately 

following a blast and dissipate quickly. 2) Stress-induced events are more randomly distributed. 

They occur at larger time delays following blasts, often hours or days. Such events are generally 

located remote from excavations and are often associated with geological structure though they 

need not be related. It is this second category that is of interest since the time and location of such 

events are not predictable. Within Creighton Mine such events occur in a distinct zone 

surrounding the main excavation. 

41

Figure 3.1 (A) Plan view of events related to development blasts (blasts not shown) along the 7810 

exploration drift; and (B) production blast-induced events related to blasting in the 4247 Sill. 

Full waveform recording allows for the calculation of additional seismic event parameters from 

waveforms recorded in the time domain or from spectra in the frequency domain (Gibowicz and 

Kijko, 1994; Mendecki, 1997). At Creighton Mine, parameter calculation is often automated but 

occasionally done manually (by selecting first arrivals). Calculated parameters include source 

radius, asperity radius, energy released, apparent stress and stress drop. The maximum particle 

displacement, velocity and acceleration can also be calculated from each waveform. 

3.2.1 Seismic Event Parameters 

A subset of 11,541 microseismic events that occurred between January 1, 2006 and December 31, 

2007 and between 7000 and 7600 feet depth was used to establish background seismic parameter 

values. This depth range eliminates dense activity related to development on deeper levels. 

Events having location errors greater than 30 feet were filtered from the dataset to avoid intrinsic 

error in calculated source parameters. Within this block, seismicity pertaining to the 7200 Level, 

7400 Level and 7530 Level was examined for spatial and temporal trends. Trends in seismic 

event parameters were also assessed. 

42

Microseismic events of this subset have an average location error of 18 feet. Events were 

recorded on average by 22 sensors (15 uniaxial and 6 triaxial sensors triggered on average) with 

the minimum condition of 8 sensors needed for an event to be recorded. Complete population 

statistics, including those for magnitude events and events identified as blasts can be found in 

Appendix B. These parameters are automatically calculated by the mine using ESG software, and 

first arrivals for microseismic events are usually automated. Statistics for macroseismic events 

that are derived from the underground array may not reflect the true magnitude of the parameters 

because of waveform clipping for stronger events. 

3.2.1.1 Moment Magnitude (M) 

Three magnitude estimates are made for microseismic events: uniaxial magnitude, as determined 

from uniaxial sensors, triaxial magnitude and moment magnitude. Magnitudes in this thesis for 

microseismic events make reference to the moment magnitudes. 

Detected microseismic events within the study area range in magnitude from M = -2.3 to M = 0.8 

with a mean of M = - 1.09. The distribution of magnitudes peaks at M = -1.3 (Fig. 3.2). Below 

this magnitude a higher proportion of events is expected but events are not recorded due to the 

detection threshold of the sensors and the minimum sensor requirement for recording events. The 

magnitude range can also be examined with the frequency-magnitude relation (Fig. 3.3). The 

shallow slope at low magnitudes demonstrates that events below M = -1.3 are infrequently 

recorded, though these are expected to occur. Beyond M = 0.4 the relation breaks down due to the 

relative infrequency of larger events as well as the recording limitations of the sensors. At high 

magnitudes, sensors become saturated and recorded waveforms clipped. The effective range of 

microseismic coverage is therefore between M = -1.3 and M = 0.4. Spatially, high-magnitude 

microseismic events do not show preferential clustering except near blast sites. 

43

Distribution of Microseismic Event 

Magnitudes 

1600 

1400 

1200 

1000 

800 

600 

400 

200 

0 

-2.5 

-2.1 

-1.7 

-1.3 

-0.9 

-0.5 

-0.1 

0.3 

0.7 

Frequency 

Moment Magnitude 

Figure 3.2: Distribution of Microseismic Event Magnitudes between January 1, 2006 and December 31, 

2007 recorded between 7000 and 7600 feet depth. 

Magnitude-Frequency Relation 

4.5 

4.0 

Log(Cumulative Frequency/yr.) 

3.5 

3.0 

2.5 

2.0 

1.5 

1.0 

N = -1.12M + 2.53 

N = -1.77M + 2.27 

0.5 

0.0 

-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 

Magnitude (M) 

Figure 3.3: Frequency Magnitude Relation for microseismic events recorded between 7000 and 7600 feet 

during the January 2006-December 2007 period. N = cumulative number of events (logarithm). Trend lines 

have been added to show relation slope. 

44

3.2.1.2 Seismic Energy (E o ) and Seismic Moment (M o ) 

The seismic moment (M o ) is a measure of event size and strength. Seismic energy, E o , is a 

measure of the total elastic energy radiated during fracture and frictional sliding (Gibowicz and 

Kijko, 1994; Mendecki, 1997). 

Microseismic events have lower energies and seismic moments compared to blasts or 

macroseismic events. This is also a spatial trend: events immediately west of the excavation in 

proximity to production blasts have high event energies and seismic moments (Fig. 3.4). Events 

located to the southwest of the excavation have lower energies compared to blast-related events 

but higher energies as compared to the remaining events south to southeast of the excavation. 

Figure 3.4: Map of the 7400 Level showing the distribution microseismic event energy. The excavated 

area is outlined in black. The colour of the event epicenters corresponds to event energy. The colour scale 

is logarithmic and represents energy in Joules. 

45

3.2.1.3 Energy Ratio, E s /E p 

The ratio of S-wave to P-wave energy (E s /E p ) is commonly used to identify source mechanisms. 

Events with high E s /E p ratios are most likely caused by shear failure along a geological structure 

while lower ratios may have a complex or dilational component of failure (Gibowicz and Kijko, 

1994). While traditionally the cutoff for E s /E p is 10 (Gibowicz et. al, 1991) for discriminating 

between extensional blast events (E s /E p 10), this value is too 

large to discriminate between shear and extensional microseismic events. A cut-off of E s /E p = 5 is 

deemed appropriate for Creighton Mine because the mean E s /E p of microseismic events is 8.6, for 

macroseismic events is 16.3, and for blasts is 6.2 (Fig. 3.5). Previous work in Creighton Mine by 

Vasak (n.d.) also deems an E s /E p ratio of 5 to be appropriate for Creighton Mine. Microseismic 

events having high E s /E p are randomly distributed, rather than being located along large 

discontinuities as would be expected from fault slip. No spatial trends were identified for events 

between the 7200 and 7530 Levels and thus no correlations between E s /E p and geological structure 

are made. Spatial distributions of detected E s/ E p events can be found in Appendix B. 

Frequency (% of total) 

35 

30 

25 

20 

15 

10 

5 

2006 Blast and Event Distribution (% of Total) 

Blasts 

Events 

0 

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 

Es/Ep 

Figure 3.5: Es/Ep ratios measured for 2006 events and blasts. The cut-off of 5 is shown by the dashed line. 

46

3.2.1.4 Stress Parameters 

Stress parameters quantified from event spectra (Mendecki, 1997) include static stress drop, 

dynamic stress drop and apparent stress. Static stress drop, 

, is defined as the average 

difference between the initial and final stress levels over a fault plane (Gibowicz and Kijko, 

1994). Dynamic stress drop, 

d 

, is the effective stress representing the difference between the 

initial stress and the kinetic friction level on a fault (Gibowicz and Kijko, 1994). The apparent 

stress, is proportional to both the seismic energy and the seismic moment: 

a 

, (Equation 3.1) 

where μ is the shear modulus of the source medium, E is the seismic energy and M o is the seismic 

moment. The distribution of event stress parameters displays similar spatial trends as energy and 

seismic moment with low parameter magnitudes to the south and south east of the excavation, 

higher parameter magnitudes to the southwest of the excavation, and elevated values where 

mining took place in the easternmost stopes during the time span under analysis (Appendix B). 

3.2.1.5 Source Dimensions 

Calculated source dimensions include source radius, r o , and asperity radius r a . These values are 

derived from spectral parameters and based on a dynamic circular fault model (Madariaga, 1976). 

Such calculations are thus highly dependent on modeled spectra (Gibowicz and Kijko, 1994). 

Large source radii occur to the west of the excavation. Clustered events to the southwest of the 

excavation have small source radii while low to intermediate values exist to the south and 

southeast of the excavation. Asperity radii are largest to the east of the excavation and more 

variable south of the excavation away from blasting. 

47

3.2.1.6 Peak Acceleration Parameter, Velocity Parameter and Maximum Displacement 

Calculated motion parameters include peak acceleration, peak velocity and maximum 

displacement. The spatial distribution of stress parameters shows the same trends as the stress and 

source dimension parameters: low parameter values are observed to the south and southeast of the 

excavation; while higher parameter values are found to the southwest of the excavation, and 

elevated values directly east of the excavation where blasting occurs. 

3.2.2 Spatial and Temporal Event Clustering 

Microseismic events tend to cluster spatially and temporally. Events that cluster in space and time 

can result from a localized increase in differential stress (Mendecki, 1997). Clusters of 

microseismic events typically follow a large event, such as a rockburst or a blast. 

Spatial and temporal trends were studied in data surrounding the 7200, 7400 and 7530 levels. 

Levels below the 7530 Level were omitted from analysis since microseismic activity reflected 

development, making it difficult to distinguish between blast-induced and stress-induced events. 

Event frequency is observed to increase with depth, including the number of macroseismic events. 

Exceptionally high rates of seismicity on and below the 7680 Level reflect active level 

development in the Deep. 

Analysis is concentrated on events to the south of the 400 Orebody excavation (shown previously 

in Figure 2.5). This population has good sensor coverage, exhibits low location error and occurs 

away from blasts. Dense event clusters directly to the east and west of the excavation are 

attributed to production blasts from outward excavation (Fig. 3.6A). Events to the north of the 

excavation are located outside the network, resulting in high location errors (Fig. 3.6A). Poorly 

48

located events were removed from clustering analyses by filtering events by error using a cut-off 

of 30 feet. The distribution of macroseismic events is shown in Fig. 3.6B for comparison. 

Seismicity that is not directly related to blasting and extraction tends to occur south of and remote 

to the excavation. Microseismic events are mostly restricted to a distinct zone extending from the 

southeastern corner of the excavation to approximately 300 feet south of the excavation. Very 

little seismic activity occurs directly south, southwest and north of the excavation. These trends in 

seismicity pertaining to the 7200 Level, 7400 Level and 7530 Level are shown in Figure 3.7. 

Events do not tend to align with mapped geological structures but rather occur in proximity to 

both shears and openings. Events on the 7200 Level appear to align with the 402 Shear Zone but 

also occur in close proximity to excavations. Macroseismic events are often attributed to fault 

movement by mine staff. Macroseismic events within the study area appear randomly distributed 

and do not cluster or conform to geological structure (Fig. 3.6B). Areas of dense microseismic 

activity are generally related to these events; spatial and temporal clustering of microseismic 

events tends to occur following a macroseismic event. Macroseismic events tend to have little to 

no precursory seismicity followed by high rates of seismicity that decay to background levels over 

a matter of hours or days, sometimes including additional macroseismic events. A review of 

rockbursting in Creighton mine by Blake and Hedley (2003) agrees that macroseismic events in 

Creighton that are expressed as rockbursts are almost always unexpected; events do not occur at 

regular intervals and do not have seismic precursors. 

49

Figure 3.6: (A) Distribution of detected microseismic events during 2006-2007 surrounding 7400 Level. 

Colour scaling represents location error with warm colours indicating increased error. The 400 Orebody is 

located within the excavation and is outlined in Figure 2.5. The skew of production-related events reflects 

the position of events relative to microseismic network. Events having a high error are further removed 

from the network; (B) Distribution of macroseismic events surrounding 7400 Level. 

50

Figure 3.7: Detected seismicity corresponding to levels 7200, 7400 and 7530 respectively. Events have 

been filtered by location error (< 30 ft.) and by depth and are restricted 50 feet above and below the level. 

Colour scaling represents moment magnitudes between M= -1.5 and M= 0.5. 

51

A dense event cluster occurs in the vicinity of the 461 orebody (orebody shown in Fig. 2.4A, B), 

which is hosted in the 461 Splay that connects the 402 and Return Air Raise shear zones. This is 

represented by clustering about the 461 Orebody on the 7530 level and is also reflected on the 

7400 Level (Fig. 3.7). 461-related seismicity does not cluster temporally but occurs sporadically 

throughout the 2006-2007 time interval, contemporaneously with events to the east in the active 

zone. Seismicity in this vicinity has also intensified from 2002-2007. This cluster is discussed in 

the following sections. 

3.2.3 Cluster Analysis for the 7400 Level 

The degree of damage in a rock mass can have a dramatic effect on the properties of the seismic 

waves emitted from microseismic sources, notably on wave velocity and attenuation (Feustel, 

1998). Such changes have been used to describe the rock mass character. Lower velocity and 

higher attenuation is recorded in a heavily fractured rock mass as compared to a homogeneous and 

unfractured rock mass (Feustel, 1998). Given this, it is expected that the state of damage in the 

rock mass would also have a noticeable effect on source parameters, most of which are calculated 

directly or indirectly from the recorded waveforms. Temporal trends in seismic event parameters 

can approximate loading curves similar to those traced in acoustic emission tests (Coulson and 

Bawden, 2008). Such curves indicate that at the point of fracture initiation, the moment 

magnitude, seismic moment, seismic energy and apparent stress increase until the point of yield, 

at which point fractures coalesce and there is a significant drop in parameter values (Coulson and 

Bawden, 2008). The source radius and source complexity (ratio of dynamic stress drop to static 

stress drop) show a decrease in parameter values during loading and a sudden increase as the rock 

mass yields. Following this, characteristics of events in an intact and fractured rockmass are 

summarized in Table 3.1. 

52

Table 3.1: Event characteristics in an intact and fractured rock mass 

Events in intact rock mass (loading) 

• High moment magnitude, M • Low M 

• High seismic energy, E o • Low E o 

• High seismic moment, M o • Low M o 

• High apparent stresses, σ a • Low σ a 

• Low source radius, R o • High R o 

• Comparable dynamic and static stress drop 

values (low complexity) 

Events in yielded rock mass (post-peak) 

• High dynamic stress drop as compared to static 

stress drop (high complexity) 

Spatial and temporal analysis of microseismic event parameters was conducted to identify trends 

and assess rockmass properties on levels 7200, 7400 and 7530. Temporal analysis of levels and 

clustered events on the 7400 Level did not reveal any significant trends (temporal parameter 

results can be found in Appendix B) but did reveal comparable spatial event distributions: dense 

seismicity extends from the southeastern corner of the excavation to an area southwest of the 

excavation (Fig. 3.7). Events in this area occur sporadically during the two-year time period. It is 

postulated that in the Creighton Deep the microseismic event distribution as well as the event 

parameters reflect both local stress conditions and the physical state of the rock mass; heavily 

damaged rock is expected to be aseismic, whereas a actively yielding rock mass will result in 

denser seismic activity. 

Seismicity on 7400 Level is separated into three distinct clusters (Table 3.2, Fig. 3.8). The first 

cluster (Cluster 1) is located to the southwest of the excavation. Cluster 1 is the densest cluster and 

has a markedly different seismic character from the other clusters. Cluster 1 contains elevated 

source parameter values for seismic moment, energy, apparent stress, stress drop as well as 

particle motion parameters that are well above background levels (Table 3.3). 

53

Clusters 2 and 3 are located to the south and southeast of the excavation and generally have lower 

source parameter values that are nearer to background levels. The implications of this are 

discussed in section 3.2.4. 

Table 3.2: Spatial cluster positions 

Range Cluster 1 Cluster 2 Cluster 3 

Northing (ft.) 6090-6273 6155-6270 6130-6225 

Easting (ft.) 4250-4440 4560-4670 4685-4810 

Depth (ft.) 7350-7450 7350-7450 7350-7450 

Figure 3.8: Three clusters are isolated for events between January 1, 2006 and December 31, 2007 located 

about the 7400 Level. Events cluster spatially but not temporally. 

54

Table 3.3: Summary of relevant parameter mean values and standard error for each cluster as compared to 

background parameter values. An asterisk (*) indicates the log of the values for scaling purposes. 

Parameter (Mean) Cluster 1 Cluster 2 Cluster 3 7400 Level Background 

Moment Magnitude (M) -1.11 ± 0.01 -1.28 ± 0.02 -1.37 ± 0.03 -1.11 ± 0.01 -1.09 ± 0.00 

Seismic Moment* (Nm) 7.70 ± 0.02 7.37 ± 0.03 7.23 ± 0.05 7.81 ± 0.02 7.79 ± 0.01 

Seismic Energy*, (J) 3.38 ± 0.04 1.73 ± 0.07 1.31 ± 0.08 2.63 ± 0.03 2.51 ± 0.01 

Source Radius (m) 2.10 ± 0.02 2.24 ± 0.04 2.55 ± 0.07 2.64 ± 0.02 2.71 ± 0.01 

Asperity Radius (m) 0.60 ± 0.01 0.59 ± 0.01 0.49 ± 0.01 0.66 ± 0.01 0.71 ± 0.00 

Es/Ep 8.89 ± 0.20 7.52 ± 0.28 9.42 ± 0.32 8.21 ± 0.18 8.62 ± 0.07 

Static Stress Drop* (Pa) 6.84 ± 0.02 6.11 ± 0.03 5.86 ± 0.04 6.05 ± 0.35 6.24 ± 0.09 

Dynamic Stress Drop* (Pa) 7.12 ± 0.02 6.50 ± 0.02 6.49 ± 0.03 6.88 ± 0.01 6.80 ± 0.01 

Apparent Stress* (Pa) 6.05 ± 0.02 4.92 ± 0.04 4.64 ± 0.05 5.37 ± 0.02 5.27 ± 0.01 

Maximum Displacement (m) -3.56 ± 0.02 -4.21 ± 0.03 -4.30 ± 0.04 -3.79 ± 0.01 -3.84 ± 0.01 

Peak Velocity Parameter (m/s) -1.36 ± 0.02 -2.01 ± 0.03 -2.09 ± 0.04 -1.59 ± 0.01 -1.62 ± 0.01 

Peak Acceleration Parameter 

(m/s 2 ) 

6.02 ± 0.02 5.40 ± 0.02 5.39 ± 0.03 5.77 ± 0.01 5.70 ± 0.01 

3.2.4 Seismicity and Rockmass Degradation 

In the mine environment, high event rates and dense event spacing suggest progressive damage of 

the rock mass and increased seismic hazard (Vasak et al., n.d.). The occurrence and 

characteristics of seismic events can be used as an indication of the physical state of the rock 

mass. Temporal trends in seismic event parameters indicate that the rockmass passes through five 

phases in the degradation process (Coulson and Bawden 2008): 

1. Crack closure and fracture initiation 

2. Fracture interaction 

3. Fracture coalescence (yield) 

4. Fracture localization (peak) 

5. Disassociation (post peak behaviour approaching the residual rockmass strength). 

Observations by Coulson and Bawden (2008) in several mines in Northern Ontario demonstrate 

that the rock mass immediately surrounding an excavation is in a state of permanent strain 

(disassociation) and is aseismic. The rock mass further from the excavation is continually 

55

fractured and behaves as a rock mass under pre-peak conditions. Similarly, the rock mass in the 

Creighton Deep can be divided into three zones based on the characteristics of seismicity (Fig. 

3.9): 

Figure 3.9: Sketch depicting location 

of (A) Yield Zone, (B) Damage Zone 

and (C) Intact Zone. Major principal 

stress is oriented East-West 

a) Yield Zone 

The yield zone occurs adjacent to the excavation to the north and south. It is the result of damage 

directly incurred by mining. Here the rock mass has undergone seismic softening (sustained 

degradation through seismic activity) and is heavily fractured. Progressive damage has resulted in 

permanent strain, low stress and has rendered this zone aseismic. The shape of the damage zone 

reflects both the shape of the excavation and the stress tensor, in which the maximum principal 

stress is near-horizontal and oriented east-west. 

Little to no seismicity occurs immediately north or south of the excavation. The rock mass in this 

area is less confined and is expected to have been degraded by mining activity, classifying it as the 

Yield Zone. Gravity-driven failure (fall of ground) occurs in this region and results from seismic 

shaking (Vale Inco, pers. comm., 2009). 

56

) Damage Zone 

The rock mass in the Damage Zone has been progressively weakened by continued seismicity. 

This area is subject to high stress and is a zone of fracture growth and localization. Rock 

undergoing strain softening has slow rupture velocities and results in small stress releases (small 

stress drops), low seismic moments as compared to failure, small energy releases (E o ) and small 

apparent stresses (Mendecki, 1997). 

Clusters 2 and 3 have seismic event parameters comparable to those expected in the Damage 

Zone. The rock mass in the vicinity of clusters 2 and 3 has been progressively degraded by 

seismic activity and is assigned to this zone. A series of rockbursts associated with unsupported 

ground surrounding old ventilation infrastructure contributes to seismicity in Cluster 3 (Vale Inco, 

pers. comm., 2009). This approximates post-peak conditions described by Coulson and Bawden 

(2008). 

c) Intact Zone 

The Intact Zone is remote from mining and the stress influence of the excavation. This zone is 

subject to background stresses and experiences low rates of seismic activity (the presence of 

drifts, ramps etc. is not considered in this simplified model). Events occurring beyond the 

nucleation zone have faster rupture velocities and are more energetic (Mendecki, 1997). 

Cluster 1 exhibits high seismic parameter values, as expected for the Intact Zone. Sustained 

seismicity (2000 through 2008) in this area corresponds to mining of the Plum Orebody (shown as 

the 6100 Orebody in Figure 2.4) on upper mine levels. An increase in event density in Cluster 1 

during the 2006-2007 time period corresponds to the onset of mining in the 461 Orebody (shown 

in Figure 2.4), which was mined in stopes from the 7680 Level to the 7755 Sublevel. 

57

The increase in event parameter values as compared to background values is associated with the 

state of the rock mass. It is assumed that the rock mass in the vicinity of Cluster 1 prior to mining 

of the 461 Orebody was in an intact state and is now subject to stress loading. Induced stresses 

from the onset of mining in the 461 Orebody (Fig. 2.4A, B) stimulated fracture nucleation, growth 

and rupture. Seismicity in this zone represents an active transition from an intact rock mass to a 

damaged rock mass. Since this rock mass is remote to the main excavation, it has not been 

exposed to the prolonged induced stress of the excavation and thus has not yet degraded to the 

state of the rock mass hosting clusters 2 and 3. This area continues to be a source of macroseismic 

events. 

3.3 Focal Mechanisms 

Recorded waveforms from mining-induced events can be utilized to characterize the failure mode 

at the source, known as the focal mechanism. Simple shear events can be characterized using 

fault plane solutions and more complex events can be described by the moment tensor. 

Information gathered from these methods can then be used to estimate the stress tensor. 

3.3.1 Fault Plane Solutions 

Fault plane solutions are a graphical representation of a fault-slip event and integrate geological 

knowledge and seismic signals. Solutions are dependent on the polarity of P-wave first arrivals 

that are recorded at a number of stations. The focal mechanism can be represented on a stereonet 

(Fig. 3.10) by plotting first arrival polarities and fitting nodal planes to define compressional and 

dilatational quadrants. If the fault plane is unknown, the fault plane solution is ambiguous as two 

solution planes exist. Pressure axes (P-axes) are oriented in the direction of maximum 

compression, tension axes (T-axes) are orientated in the direction of maximum tension and null 

axes (B-axes) are oriented along the intersection of the nodal planes. P- and T-axes plot in the 

58

quadrants of dilatation and compression, respectively) and are oriented orthogonal to each other 

and 45° to the nodal planes (Fig. 3.11; Stein and Wysession, 2003. P- and T-axes approximate 

maximum principal stresses, though these can differ significantly if failure occurs along preexisting 

structure (Gephart and Forsyth, 1984). 

Figure 3.10: Block model of a shear-slip event and corresponding focal mechanism and waveforms, 

modified from Stein and Wysession, (2003). 

Solutions are limited to pure shear event mechanisms only, that is, mechanisms with doublecouple 

sources. Double couple (DC) sources have source radiation patterns that can be described 

by coupled forces with no net torque (Fig. 3.11; Stein and Wysession, 2003). 

Figure 3.11: (Left) coupled forces along fault and auxiliary planes; (middle) paired force couples (doublecouple); 

(right) resultant fault plane solution, where shaded quadrants are in compression. Modified from 

Stein and Wysession, (2003). 

Events involving interaction between more than one fracture, volume change and those having 

mixed mechanisms cannot be represented using the fault plane solution method (Miller et al., 

1998; Stein and Wysession, 2003). Voids created by mining often cause extension and thus non- 

59

double couple events. As a result, a large number of events within the mine environment cannot 

be characterized with this method but are better represented as a moment tensor. A poor fit of 

fault planes to plotted first arrivals may also arise as a result of the event being detected by a low 

number of sensors, poor first polarity picks, source location error or the homogeneous velocity 

model used by the mine. To relate microseismicity to structure, fault plane solutions for 

macroseismic and microseismic events corresponding to the 7400 Level were generated and 

analyzed for common faulting mechanisms. 

3.3.1.1 Fault plane solutions for macroseismic events 

Although macroseismic events saturate the underground network, first arrivals are well recorded 

and their polarities preserved, allowing for fault plane analysis. P-axes, T-axes and nodal planes 

were estimated for 93 events with adequate statistical and visual double-couple solutions. Fault 

plane solutions and calculated fits were generated using the grid search algorithm in the program 

VFps by the Engineering Seismology Group. This method returns the best fit (between 0 and 

100%) which has the least error. Events are located between the 7400 Level and 7810 Level but 

are mostly confined to the south of the main excavation on the 7400 and 7530 Levels. These 

occurred during the 2006-2007 time span. Plotted P- and T-axes and nodal planes for these events 

do not show consistent axes or mechanism types (Fig. 3.12); poles to nodal planes do not form 

distinct clusters and no common axes are revealed (Fig. 3.13). A sample of fault plane solutions 

for macroseismic events corresponding to the 7400 Level is shown in Figure 3.14. 

60

Figure 3.12: Lower hemisphere equal area stereonet diagram depicting the orientation of (A) P-axes for 

macroseismic fault plane solutions; (B) T-axes for the same 96 events. 

Figure 3.13: Lower hemisphere equal area stereonet diagram depicting (A) Possible fault planes and (B) 

poles to planes for 93 mechanisms (186 planes and poles) for the 7400 Level. 

61

Figure 3.14: Sample fault plane solutions for macroseismic events corresponding to 

the 7400 Level, January – December 2007. Grey quadrants represent compression and 

white quadrants represent dilatation. Each triangle represents the polarity of the first 

arrival at a sensor. 

3.3.1.2 Fault plane solutions for microseismic events 

Fault plane solutions were generated for 196 microseismic events during the 2006 time period, 

belonging to the 7400 and 7530 Levels. Solution planes and axes for individual events can be 

found in Appendix C. The chosen events have low location errors (less than 30 feet), good 

statistical fits for fault planes as well as adequate visual fits. Fault plane solutions have an average 

fit of 77%. Fault plane solutions and calculated fits were generated using the program VFps by 

the Engineering Seismology Group. Discarded events include those that do not fit a doublecouple 

solution, events with poor focal sphere coverage and events with poor first polarity picks. 

P-axis, T-axis and B-axis attitudes (as shown on Fig. 3.11) plotted on a lower hemisphere 

stereonet form broad clusters (Fig. 3.15). Classification of failure modes using the focal 

62

mechanism shows that over 57% of the events have predominant strike-slip mechanisms (Fig. 

3.16) while the remaining mechanisms represent either primarily reverse, dip-slip or strike-slip 

failures. Though fault mechanism types have little meaning in the underground environment, mechanism 

types show consistency. Strike-slip mechanisms share similar P- and T-axis orientations and have 

similar axis clusters as those plotted in Figure 3.15, suggesting slip along favourably oriented 

fractures. For such events, P-axes plunge shallowly to the west; T-axes trend plunge shallowly to 

the north; while B-axes are near vertical. 

The similarity in axis orientation suggests that while some slip occurs on randomly oriented 

fractures, lateral slip preferentially occurs on steeply dipping NNW or ENE striking 

discontinuities. No absolute discrimination between the fault plane and auxiliary plane can be 

made. The strike of the ENE-oriented fault plane solution is similar to the strike of the 118 Fault 

System, though the dip direction is opposite. If movement should occur along this ideal fault 

plane, the solution suggests that motion would be dextral. If strike-slip movement were to occur 

along the NNW-trending plane, motion would be sinistral. The representative mechanism, plotted 

using average P-, B- and T-axis orientations, is shown in Figure 3.17. 

63

Figure 3.15: Contoured focal mechanism axes for the 7400 and 7530 Level. Lower Hemisphere, Equal 

angle plots contain 196 points. (A) Contoured P-axes; (B) contoured B-axes; (C) and contoured T- axes. 

64

Figure 3.16: Classification of principal event mechanism type, levels 7400 and 7530. 

Figure 3.17: Approximate representative focal plane solution and corresponding fault plane solution 

kinematics based on average P-, B- and T-axis orientations. Shaded quadrants represent compression and 

white quadrants represent dilatation. 

65

Axes for event clusters 1 and 2 are presented for comparison in Figures 3.18 and 3.19. T-axes for 

Cluster 1 events have similar trends but steeper dips, while B-axis trends vary in orientation from 

NNE-trending and with shallow plunges to near-vertical. 

3.3.1.3 Fault Plane Solution Discussion 

Event mechanisms do not show a direct correlation to mine-scale faults. Event mechanism types 

are distributed over the study area (Fig. 3.20) and do not cluster or align with individual faults. 

The distribution of event mechanism types thus does not allow the neokinematics of specific faults 

to be determined and does not suggest fault activity. 

Microseismic event mechanisms show consistency in P- and T-axis orientations, suggesting 

reactivation of preferentially oriented fractures. Lack of consistency in macroseismic event 

solutions suggests that failure does not localize along shear zones in the Creighton Deep. This 

inconsistency instead indicates more variation in the geometry of failure surfaces. Alternatives to 

fault-slip are proposed: 

 

Macroseismic events may embody the breaking of asperities between existing fractures or 

weak zones. This can occur along variably oriented pathways and in different faulting 

styles. 

 

Joints and preexisting fractures in the rock mass may interact to form a slip radius 

sufficiently large to accommodate large magnitude events. 

Coulson (1996) postulated that slip between the 6600 and 7200 Levels in Creighton Mine 

occurred along networked joint planes rather than on faults. Coulson (1996) concluded that 

seismicity in the Creighton Deep is related to the rock mass joint fabric and is the result of 

mining-induced stresses. 

66

Figure 3.18: Contoured P-axis, B-axis and T-axis orientations for events within Cluster 1. 

67

Figure 3.19: Contoured P-axis, B-axis and T-axis orientations for events within Cluster 2. 

68

Figure 3.20: Distribution of double-couple event mechanism types on the 7400 Level. 

In conducting fault plane solution analysis, a number of events were discarded that did not have 

adequate statistical or visual fits. Failure to fit a double-couple solution can be a result of either 

(or both) the fault plane solution method or the physical failure process. Poor solution fits can be 

a result of poor focal sphere coverage, poor first arrival picks, uncertainty in first arrival polarities 

or insufficient polarity information (Urbancic and Young, 1995). 

Poor solution fits can also be obtained if the solutions do not have a double-couple solution. Nondouble-couple 

solutions are a result of the physical failure process and occur when the moment 

tensor contains components other than pure shear, such as volume change. Blasts, for example, 

cause large volumetric changes and result in non-double-couple mechanisms. Deviations from the 

double-couple solution are expected in the mining environment since a number of free surfaces 

exist along which fractures can interact during failure. Intersections of fractures and openings, 

complex interactions between fractures as well as closely spaced failures in time and space are 

69

expected to be responsible for a large number of non-double-couple mechanisms observed in 

Creighton Mine. 

3.4 Stress Tensor Inversion 

P-, T- and B-axes derived from focal mechanisms can be used as a crude approximation to 

principal stress orientations. Axes represent the ideal stress orientations for a given solution. In 

the presence of preexisting fractures, the maximum principal stresses may differ significantly 

from P- and T-axes and be oriented elsewhere in compressional and dilatational quadrants 

(Gephart and Forsyth, 1984). Indeed in Creighton Mine faults and fractures are oriented obliquely 

to principal stress directions, which may cause the P-, T- and B-axes to differ from principal stress 

orientations. 

One way to resolve the local stress tensor is through stress tensor inversion. Inversion was done 

with software developed by Gephart (1990). Details of the inversion method are described in 

Gephart and Forsyth (1984) and the program is presented in Gephart (1990). The software makes 

use of P- and T-axis measurements and compares different solutions to find the best fit between 

the predicted model and actual data with minimal error. 

P- and T-axes from 95 focal mechanisms for events located in proximity to the 7400 Level were 

used for inversion. Results from this inversion indicate that the maximum principal stress is near 

horizontal and oriented E-W and the minimum principal stress trends SSE and has a moderate 

plunge (Fig. 3.20). The best model was that with a minimum misfit of 10.62º (Fig. 3.21). The 

parameter R ranges between 0 and 1 and is defined as: 

 

 

2 1 

R (Gephart and Forsyth, 1984). (Equation 3.2) 

3 

1 

70

This parameter reflects the magnitude of intermediate principal stress relative to the maximum or 

minimum principal stress (Bellier and Zoback, 1995). As the magnitude of the intermediate 

principal stress approaches that of the maximum principal stress, R approaches 0 and is indicative 

of an extensional stress regime; as it approaches the minimum principal stress, R approaches 1 and 

the rock is increasingly confined, indicative of a compressional regime (Bellier and Zoback, 1995; 

Bellier et al., 1997). Inversion for events on the 7400 Level yields R = 0.5 which indicates pure 

strike-slip failure. 

Stress orientations are comparable to the regional stress tensor, discussed in section 3.4.1. Stress 

inversion was also performed for localized clusters of events, Cluster 1 and Cluster 2, as 

previously defined. This was conducted using the exact solution method (described in Gephart 

and Forsyth, 1984) and a two-degree grid to identify perturbations in the local stress field where 

dense seismicity occurs. Cluster 3 was omitted from analysis due to insufficient data. Principal 

stresses for Cluster 2 approximate those for the 7400 Level stress inversion and the regional stress 

(Fig. 3.22). Principal stresses for Cluster 1, however, differ significantly from the regional stress. 

The inversion results with the minimal misfit identify a steeply-plunging maximum principal 

stress and a near-horizontal minimum principal stress (Fig. 3.23). An additional minimum 

principal stress axis that trends north is also identified. A second stress inversion for Cluster 1 

events (Fig. 3.24) shows two distinct stress orientations, though this solution has a slightly higher 

misfit from the previous solution (8.12 o , as compared to 7.63 o ). R parameter values for Cluster 1 

of 0.05 and 0.10, respectively, demonstrate that the rock mass is under extension (uniaxial 

eccentric compression). Rotation of the stress tensor in proximity to Cluster 1 may be responsible 

for high magnitude, high energy events, though the cause for this change is unclear. 

71

Figure 3.21: Results of focal mechanism stress inversion for 95 events around the 7400 Level. Numbered 

results correspond to maximum principal stresses (1 = sigma 1). 

Figure 3.22: Stress inversion for Cluster 2 focal mechanisms. 

72

Figure 3.23: Preliminary stress inversion for Cluster 1 focal mechanisms. 

Figure 3.24: Secondary stress inversion for Cluster 1 focal mechanisms. 

73

3.4.1 Stress Tensor Discussion 

The estimated maximum principal stress orientations are comparable to regional stress 

orientations as measured in Creighton Mine (Cochrane, 1991) and to the calculated stress tensor 

(Coulson, 1996; Bawden and Coulson, 1993). A comparison of stress orientations is shown in 

Table 3.4 and spatial relationships are displayed in Figure 3.25. 

Table 3.4: Comparison of maximum principal stress orientations from various sources 

Source 

σ-1 σ-2 σ-3 

Trend Plunge Trend Plunge Trend Plunge 

Calculated Stress Tensor 281 20 018 17 145 63 

Coulson, 1996 

Measured Stress, 7000 L, 270 20 013 32 152 51 

Cochrane, 1991 

Inversion Results 

265 18 007 33 151 51 

(7400 L, Misfit 10.62) 

The close proximity of principal stress orientations indicates that the local stress tensor 

responsible for induced failures within Creighton Mine is compatible with the regional stress 

tensor. Individual stress measurements however show considerable variation in orientation (Fig. 

3.26). The exception is the events located in Cluster 1. 

74

Figure 3.25: Equal area stereonet showing proximity of principal stress 

orientations calculated from fault plane solutions to stress orientations derived 

from measured and calculated stresses, as summarized in Table 3.4. 

Figure 3.26: Stress measurements as reported by Bawden and Coulson (1993). Data is taken from levels 

6800 and 7000 and includes 3 CSIR (Council for Scientific and Industrial Research) triaxial cell 

measurements; 3 CSIRO (Commonwealth Scientific and Industrial Research Organization) hollow 

inclusion cell measurements; 1 biaxial strain rosette (doorstopper) measurement. 

75

Although principal stress axes can vary significantly from P-, B- and T-axes, similarities exist 

between axis orientations. 

The maximum principal stress orientation agrees with P-axis 

orientations (Fig. 3.27A). The intermediate and minimum principal stresses also align with focal 

mechanism T- and B-axes. The intermediate stress, however, corresponds to the orientation of the 

T-axis, and the minimum principal stress with null axis (Fig. 3.27B, C). 

A near-horizontal maximum principal stress and near-vertical minimum principal stress should, by 

Andersonian fault theory (Anderson, 1951), produce reverse faults. New failures would be 

expected to exhibit reverse-sense kinematics. Indeed shallow fractures were observed to have 

reverse displacement along later fractures that intersect or displace shear zones and zones of high 

strain (as discussed in Chapter 2). However, strike-slip mechanisms predominate, producing 

mechanisms with different axis orientations. Strike-slip ruptures are also much more favourable 

given the steep fault geometry and attitude with respect to the stress tensor. Strike slip failures 

along steeply-dipping faults in Creighton Mine have been noted by Cochrane (1991). 

Strike-slip failures in Sudbury mines in a reverse regime were also observed by McKinnon 

(2006), who proposed that late stage faults subject to seismicity are in a state of critically stability. 

Minor perturbations (e.g., mining-induced stress changes such as blasts) can cause instabilities 

remote to openings. Given the variability in principal stress orientation and close proximity 

between measured intermediate and minimum stress magnitudes, small perturbations (reduction in 

sigma-2, increase in sigma 3 or both) could indeed cause strike-slip failure in an overall reverse, 

pre-mining stress regime. 

76

Figure 3.27: (A) Maximum principal stress orientations derived from stress inversion superimposed on 

contoured P-axis measurements for all 7400 Level events; (B) Sigma-2 orientations, superimposed on 

contoured B-axis measurements; and (C) orientations for Sigma-3, superimposed on contoured T-axis 

measurements for the same events. 

77

Chapter 4 

Modelling Stress in the Creighton Deep 

4.1 Introduction 

Stress in the mine environment results from a superposition of regional tectonic stresses, local 

stress induced by mining geometry and material extraction and is also influenced by the presence 

of geological structures and differences in material properties. It is impossible to model exact 

stress conditions within a mine because of the complex nature of rock and the unknown state of 

the pre-mining stress conditions. However, simplified constitutive models with specified material 

properties, initial and boundary conditions allow for insight into more complex rock mass and 

fault behaviour. 

Numerical stress analysis models of the 7400 Level at Creighton Mine were used to provide 

insight into: 

 

 

 

the influences of mining geometry and structure on stress distribution in the mine; 

the extent of the yield zone surrounding the excavation; 

and the amount of induced displacement along faults. 

The sensitivity of modelled results was assessed by varying the fault strength, selectively 

weakening faults based on geological insight and by changing boundary stress conditions. In 

doing so, constraints were placed on existing stress conditions. The ultimate goal of the numerical 

modelling is to compare modelled stress with observed seismicity and integrate geological 

knowledge of the rock mass, in order to develop an understanding of the influence of the 

structural system in the Creighton Deep on seismic behaviour. 

78

4.2 Numerical Methods 

Phase 2 and Universal Distinct Element Code (UDEC) are two numerical stress analysis packages 

that were used to model and simulate stress on the 7400 Level. Phase 2 , developed by Rocscience 

(Rocscience Inc., 2005), is a continuum code that employs the finite element method. Using this 

program the model is discretized into a mesh of triangular elements and nodes (Fig. 4.1). When 

boundary conditions are applied, displacements are computed at each node. The displacements 

within elements are used to calculate strains for each element. Strain is then translated into stress, 

integrating rockmass properties (Pande et al., 1990). The behaviour of both the continuum and 

discontinuities in this thesis is assumed to be governed by Mohr-Coulomb failure criteria. 

UDEC, developed by Itasca Consulting Group, Inc. (2000), is a 

discontinuum code that employs the distinct element method. A 

discontinuum model differs from the continuum model in that the 

Figure 4.1: Schematic 

diagram of triangular 

elements and nodes. 

model is defined by contacts and interfaces that separate rigid and/or 

deformable blocks (Cundall and Hart, 1992; Hart, 2003). UDEC 

models use a continuum mesh inside blocks. Contacts are allowed to 

interact and deform (Jing, 2003). 

Unlike the finite element method, the UDEC model allows for 

evolving contact conditions. The model proceeds through a series of time steps – a feed-forward 

process where results from the previous iterations are used for the next. UDEC works by applying 

the force-displacement law at contacts and formulating and solving equations of motion 

(Newton’s second law) for the defined blocks (Hart, 2003). Using block properties, forces and 

displacements are translated into stress and strain for each bock. As strain is accumulated, these 

quantities are recalculated and used as inputs for the next time step. As the model progresses, it 

recognizes block rotation, sliding contacts, block detachment and new interfaces between blocks 

79

(Cundall and Hart, 1992). This allows for the behaviour of the medium as well as the 

discontinuities to be modelled. Like Phase 2 , unbalanced forces must be reduced for the model to 

reach equilibrium. In this study, rock mass and fault behaviour is represented by a Mohr- 

Coulomb constitutive model. Since the Creighton Deep is pervasively faulted, discontinuum 

models were used in preference to continuum models and are discussed in this chapter. A 

discussion of Phase 2 models can be found in Appendix D. 

4.3 Model Input Parameters 

Pre-mining stress and model geometry are the main factors that influence the elastic model 

response. In plastic models, this and rock strength are an integral part of the rock mass response. 

Accurate geometry, stresses and strength parameters are thus required for models. The 

determination of these parameters is outlined in this section. 

4.3.1 Elastic and Plastic Models 

Both elastic and plastic models were developed for the 7400 Level. Elastic models have a linear 

response to stress such that deformation is recoverable (Fig. 4.2). Beyond the elastic limit, plastic 

models cannot accommodate additional stress. At this point, tractions are reduced until the rock 

mass responds by deforming in a non-recoverable manner (yields) and stress is transferred to 

surrounding rock (Duncan Fama, 1993; Falmagne, 2001, Wiles, 2006). This behaviour cannot be 

simulated using elastic models and thus elasto-plastic models are required. In such models, this 

behaviour is achieved through rock mass yielding or slip on faults, if they are present. In the 

numerical modeling packages, when stress within an element exceeds the failure criteria, the 

element yields and stress is transferred to surrounding elements (Duncan Fama, 1993; Wiles, 

2006). 

80

Stress-strain relationships are useful for describing the rock mass response on the 7400 Level. 

Remote to the excavation, rock is confined and considered to respond elastically to loading stress. 

In proximity to the main excavation where low confinement conditions exist, the rock is expected 

to behave as a plastic material when subject to continued loading. This process is nearly aseismic. 

The transition from an elastic to a plastic state is determined by the material or fault constitutive 

model, based on the relationship between stress, strain and the failure criteria. 

Figure 4.2: The stress versus strain model for an elastic, perfectly plastic material. 

4.3.2 Model Constituents and Input Parameters 

The model geometry is based on the 7400 Level geometry obtained from plans provided by 

Creighton Mine and consists of three parts (Fig. 4.3): 

1. An excavation; 

2. the rock mass surrounding the excavation; and 

3. faults intersecting the rock mass. 

81

A 

B 

Figure 4.3: (A) Complete model geometry; (B) excavation and fault geometry within inner box in (A) is 

shown with labeled discontinuities and excavation. The area outside the inner box in (A) is subject to 

boundary effects. SZ = shear zone. 

The excavation on the 7400 Level consists of backfilled and unfilled stopes and sills. These are 

modelled as one large void. This can be done under the assumption that backfill has little loadbearing 

capacity and stiffness compared to the surrounding rock mass and thus can be ignored in 

the models. Drifts and small excavations remote from the main excavation have been omitted to 

simplify the level model, as they have negligible effect on the mine-scale stress field. 

Strength parameters for the medium surrounding the excavation reflect rock mass quantities rather 

than laboratory values for intact rock, which overestimate strength (Pande et al., 1990; Schultz, 

1996). These rock mass parameters (summarized in Table 4.1), except where noted, were taken or 

calculated from estimates made by Coulson (1996) for footwall rocks in Creighton Mine. Values 

for normal and shear stiffness have been increased from calculated values to prevent contact 

overlap. The boundaries of the model, and thus the medium, are created far from the excavation. 

This ensures that modelled stress around the excavation is free from edge effects that result from 

the modelling process. 

82

Rock mass failure is governed by the Mohr-Coulomb failure envelope (Fig. 4.4). The envelope is 

defined by the equation, 

τ = σ n tan(Ф) + C, (Equation 4.1) 

where 

τ = the resolved shear stress, 

σ n = the normal stress, 

C = the cohesion, and 

Ф = the angle of internal friction. 

Both cohesion and the angle of internal friction are specified in each model. Parameters are 

consistent for the rock mass and are varied for the discontinuities. 

Field of 

Failure 

Field of 

Stability 

Figure 4.4: Mohr circle and Mohr-Coulomb failure envelope defined by cohesion and angle of internal 

friction (Ф). 

Shear zones, which dissect the rock mass, are generally schistose as compared to their granitic 

host rock. These are modeled as discontinuities with lower strength than the surrounding rock 

mass (Table 4.1). The geometry of the shear zones is simplified. The model assumes that shear 

83

zones are planar in geometry, are of uniform strength and are laterally continuous beyond the 

limits of the mine, though in reality shears may be discontinuous and have variable orientations 

and properties. 

Table 4.1: Rock mass and discontinuity model properties 

Rock mass Properties 

Discontinuity Properties 

Property Value Property Value Range 

Cohesion (C) 10 MPa Cohesion (C) 0-10 MPa 

Friction Angle (Φ) 35° Friction Angle (Φ) 10-35° 

Density † (ρ) 2965 kg/m 3 Normal Stiffness †† 700,000 MPa/m 

Young’s Modulus (E) 35 GPa Shear Stiffness †† 99,400 MPa/m 

Poisson Ratio (υ) 0.263 Tensile Strength 0-10 MPa 

Bulk Modulus * (K) 24,613 MPa 

Shear Modulus * (G) 13,856 MPa σ 1 (E-W) ††† –102.7 MPa 

σ 3 (N-S) ††† 

–73.4 MPa 

* 

Calculated 

† 

Density from Tulk (2001) 

†† 

Stiffness values increased to prevent contact overlap in UDEC 

††† 

Maximum and minimum stresses (in plane) calculated from overcoring measurements 

Two different approaches are used to load the model once the geometry, properties of the material 

and discontinuities are specified 

1. A homogeneous stress field was initiated within the model and at the boundaries 

2. Incremental displacements were used to synthesize tectonic loading 

Methods and results for both loading methods are discussed in the following sections. Boundary 

conditions for both models are depicted in Figure 4.5. 

Staged models were also created to better understand the effect of mining on the stress field and 

induced fault slip. This allowed the rock mass and faults to come to equilibrium without an 

excavation. UDEC code for the models used in this research can be found in Appendix E. 

84

Figure 4.5: (A) Model for tectonic loading. North, south and eastern boundaries are constrained such that 

motion perpendicular to the plane is restricted. A small eastward boundary velocity, ∆v, is applied to the 

western model boundary. (B) A homogeneous stress field is applied at the boundaries. All sides are 

restrained such that motion perpendicular to the plane is restricted. 

4.4 Modelling with a Homogeneous Stress Field 

When a homogeneous stress field is applied, boundary stresses are specified such that σ 1 is 

oriented east-west and σ 3 is oriented north-south. Models were initiated with internal stresses set 

equal to the boundary stress conditions. Three cases are presented for the same model geometry to 

test the sensitivity of the solution to changes in fault strength and boundary conditions. 

4.4.1 Case 1: Variable fault strength parameters 

In the first case, all faults within the model are considered to have the same properties regardless 

of geology. Four fault strength conditions are tested (Table 4.2). 1) The locked condition 

indicates that faults are strong, healed and inactive; 2) the strong fault condition indicates that 

faults are strong and cohesive, yet still weaker than the rock mass; 3) the moderately strong 

condition implies that faults have previously slipped and have lost cohesion; 4) and lastly, the 

85

weak fault condition represents a reasonable failure band fault strength used to examine the effect 

of very weak faults. 

Both elastic and plastic models are tested under these conditions. For all fault conditions, the 

model is subjected to a compressive stress field where σ 1 = –102.7 MPa and σ 3 = –73.4 MPa. 

Stress magnitudes are based on stress estimates for the 7400 Level, derived from overcoring stress 

measurements made by Creighton Mine. The negative sign convention in UDEC indicates 

compressive stress. 

Table 4.2: Fault parameters tested for Case 1. 

Fault Condition 

Cohesion Friction 

(MPa) Angle (º) 

Locked 50 50 

Strong 5 35 

Moderately Strong 0 35 

Weak 0 20 

Both elastic and plastic models for maximum stress, differential stress, slip, and yielding produce 

similar results. The locked fault condition produces low maximum and differential stresses 

immediately to the north and south of the excavation. Further from the excavation, high stresses 

form a ring around the excavation. As the cohesion is lowered at a constant friction angle, from 

the strong to the moderately strong model, maximum stress (Fig. 4.6) and differential stress (Fig. 

4.7) is enhanced to the south and southeast of the excavation and diminished to the southwest of 

the excavation. When the friction angle is very low (the weak fault case), stress is diminished to 

the south of the excavation and high stresses are pushed farther outwards away from the 

excavation. Yielding in the plastic models aligns with the strike of the 118 System shear zones 

and further slip is induced along shear zones in proximity to the excavation. 

86

The zero cohesion and low friction value (20°) condition is considered too weak to produce a 

realistic stress distribution. In this instance, the shear zones are weak enough to accommodate slip 

but the resulting magnitude of stress to the south of the excavation is diminished, whereas high 

stress is expected based on the occurrence of seismicity. 

East-west striking shear zones as well as the Footwall Shear Zone have negligible influence on 

stress distribution. The 1290 Shear Zones (and 400-East Shear Zone which is not represented in 

the model) strikes parallel to the far field stress and is thus not favourably aligned with the stress 

field to slip. Southwest-striking shear zones have the greatest impact on stress distribution; this 

system acts to redirect stress such that trends of high stress to the south of the excavation show 

alignment with the strike of the shear zones. This effect is enhanced with lower fault strength, 

though the magnitude of stress surrounding the excavation is reduced when faults are very weak. 

Displacement occurs along the Plum and Return Air Raise Shear Zones as right-lateral slip and is 

enhanced at low friction angles (Fig. 4.8). The plastic model exhibits tensile failure of the rock 

mass in proximity to the excavation with past and current yielding farther from the excavation 

(Fig. 4.9). In the strong and moderately strong cases yielding begins to localize along 

discontinuities. This effect is enhanced with lower fault strength. Stress trajectories for elastic 

and plastic models show a flow of stress around the excavation with little disturbance in the stress 

field near faults (see Appendix D). Stress orientations to the south of the excavation are 

conformable to the regional stress inversion presented in the previous chapter. 

87

Figure 4.6: Model of maximum principal stress for Case 1 for (A) elastic model and (B) plastic model. 

Faults are assigned a cohesion of 0 MPa and a friction angle of 35 degrees. Scale is in MPa. 

Figure 4.7: Model of differential stress for Case 1 for (A) elastic model and (B) plastic model. Faults are 

assigned a cohesion of 0 MPa and a friction angle of 35 degrees. Scale is in MPa. 

Figure 4.8: Model of fault slip for Case 1 for (A) elastic model and (B) plastic model. Faults are assigned 

a cohesion of 0 MPa and a friction angle of 35 degrees. 

88

Figure 4.9: Model of yielding for Case 1 for (A) elastic model and (B) plastic model. Faults are assigned a 

cohesion of 0 MPa and a friction angle of 35 degrees. 

4.4.2 Case 2: Variable Fault Strength by Shear Zone Family 

Case 2 considers families of structures that have different strength parameters based on 

underground observation (Table 4.3). Shear zones that are associated with increased seismicity 

and increased reinforcement with visible damage to mesh and/or shotcrete, indicating 

displacement, are assigned low strength parameters. Shear zones that are exposed with visible 

damage but have seemingly little seismic influence are assigned intermediate strength parameters 

and those with no visible damage or association with seismicity are assigned high strength 

parameters. 

The model is subjected to the standard compressive stress field where 

σ 1 = -102.7 MPa, oriented E–W, and σ 3 = –73.4 MPa, oriented N–S. As in Case 1, stress 

magnitudes are based on estimates for the 7400 Level from overcoring stress measurements made 

by Creighton Mine. 

89

Fault Family 

Table 4.3: Strength parameters assigned to shear families for Case 2. 

Cohesion 

(MPa) 

Friction 

Angle (º) 

Geological Description 

E–W-striking shears 5 35 No seismicity or damage 

and splays 

Footwall Shear 0 35 No Seismicity but visible 

damage 

SW-striking shears 0 20 Associated seismicity, 

damage and/or reinforcement 

necessary 

The southwest-striking fault system is interpreted to be the weakest (Table 4.3). As found in Case 

1, this fault system has the most influence on the stress field; the east-west striking shear zones 

and the Footwall Shear Zone show little influence. 

There is little difference between the modelled results for Case 2 and Case 1. Model results can 

be found in Appendix D. The moderately strong fault condition produces a realistic stress 

distribution. In both plastic and elastic models, low stresses occur adjacent to the excavation and 

high stresses (Fig. 4.10) and high differential stresses (Fig. 4.11) align with SW-striking shear 

zones to the south of the excavation. Right-lateral displacement is induced along the Plum and 

the Return Air Raise Shear Zones in this area (Fig. 4.12). In the plastic model, damage shows 

some alignment with the SW-striking shear zones to the south of the excavation (Fig. 4.13). 

Figure 4.10: Model of maximum stress for Case 2 for (A) elastic model and (B) plastic model. Faults are 


90





Figure 4.13: Model of yielding for Case 2 for (A) elastic model and (B) plastic models. Faults are 

assigned a cohesion of 0 MPa and a friction angle of 35 degrees. 

91

4.4.3 Case 3: Increased Principal Stress Ratio 

Case 3 considers the effect of increasing the principal stress ratio, k = σ 1 /σ 3 . The minimum 

principal stress, σ 3 , was lowered such that the far-field stress was increased from k=1.4 to k=2 

(note that σ 2 is oriented out-of-plane). This was done to test the sensitivity of the faults to 

boundary conditions, by increasing the shear loading on faults to induce slip. Both elastic and 

plastic models under this condition are assigned the variable properties summarized in Table 4.2. 

Modifying the principal stress ratio has the effect of only slightly modifying the stress distribution 

from that observed in Case 1. The moderately strong fault model is shown in Figures 4.17 and 

4.18. Observations from Case 3 include: 

• High maximum and differential stresses align with SW-striking shear zones to the south of the 

excavation (Figs. 4.14 and 4.15). 

• Right-lateral displacement is induced along the Plum and Return Air Raise Shear Zones to the 

south of the excavation in the elastic case and solely along the Plum Shear Zone in the plastic 

case (Fig. 4.16). 

• Plastic yielding occurs along SW-striking shear zones and is enhanced along splay structures, 

linking the Fresh Air Raise and Plum Shear Zones in the plastic model (Fig. 4.17). 

92

Figure 4.14: Model of maximum stress for Case 3 for (A) elastic model and (B) plastic model. Faults are 






93

Figure 4.17: Model of yielding for Case 3 for (A) elastic model and (B) plastic models. Faults are 

assigned a cohesion of 0 MPa and a friction angle of 35 degrees. 

4.5 Tectonic Loading Model 

In the case of the tectonically loaded model, elements are assigned a hydrostatic stress field with a 

value between the far-field maximum and minimum principal stresses, σ 1 and σ 3 . The north, south 

and east sides of the model are restrained, preventing movement normal to the boundary. It is 

loaded by applying an infinitesimal inward velocity to the free boundary to simulate tectonic 

loading, as depicted in Figure 4.5. The advantage of the tectonic model is that there is a continual 

source of boundary stress, whereas the model initiated with both boundary and internal stresses 

may experience relaxation when the excavation is introduced. The tectonic loading model was 

constructed to examine the effect of this type of loading on stress and slip along faults. 

This method of loading produces a modified stress distribution from the homogeneous stress field 

model (Fig. 4.18). Higher stresses and larger zones of high stress are concentrated to the east and 

west of the excavation. Concentration of stresses also occurs to the southeast of the excavation 

and aligns with SW-striking shear zones. This effect is less pronounced when examining the 

distribution of differential stress values (Fig. 4.19). The difference may be a result of stress 

accumulation in the tectonic loading model, as opposed to stress relaxation in the homogeneous 

94

stress field model. There is little difference in modelled fault stability; the model shows similar 

modelled fault slip (Fig. 4.20) and rock mass yielding (Fig. 4.21) as compared to models subjected 

to a homogeneous stress field (Figs. 4.6 to 4.9). 

Figure 4.18: Tectonic model for (A) elastic model and (B) plastic model. Faults are assigned a cohesion of 

0 MPa and a friction angle of 35 degrees. Scale is in MPa. 


0 MPa and a friction angle of 35 degrees. Scale is in MPa. 


0 MPa and a friction angle of 35 degrees. 

95

Figure 4.21: Tectonic model of yielding for (A) elastic model and (B) plastic models. Faults are assigned 


4.6 Modelling Rock Mass Degradation 

Seismic events occur as a result of slip on existing fractures or through the creation of new 

fractures when stress exceeds the strength of the rock mass. Seismicity can thus signal the onset 

of rock mass damage and degradation. Damage begins as a process of fracture initiation and 

progresses to a state of fracture growth and interaction as the rock mass progressively yields. 

Thresholds for both rock mass damage and yield in brittle rock can be defined by stress and 

through seismic monitoring (Falmagne, 2001). This is the same process defined using acoustic 

emission monitoring at the lab scale (Eberhardt et al., 1999). The onset of microseismicity 

indicates that stress exceeds the damage threshold and that fracture initiation has commenced; 

continued emission signals fracture propagation (Falmagne, 2001). When seismic events begin to 

cluster, this denotes that stress levels exceed the yield threshold of the rock mass. At this stage, 

fractures are numerous and long enough to interact and coalesce, causing an overall change in 

rock mass strength properties (Falmagne, 2001). High event rates as well as dense event 

96

clustering are indications of rock mass yielding and increased hazard (Vasak, n.d.). Progressive 

yielding and tensile failure will eventually render the rock mass aseismic, as the rock begins to 

behave in a plastic manner, transferring stress to the surrounding, more intact rock. 

Similar to the degradation process described by seismic event parameters in Chapter 3, the 

distribution of stress around the excavation is suggestive of a progressive damage process. In the 

yield zone, in situ strength reduction of the rock mass occurs as a result of unloading from a loss 

of confinement, stress rotation, crack-surface interaction and rock mass heterogeneity (Diederichs, 

2003). Rockmass failures caused by stress and marked by seismicity can occur along existing 

fractures or through the creation of new fractures in the damage zone beyond the yield zone. Both 

failure mechanisms are explored in the following sections by mapping slip conditions and rock 

mass degradation stress. 

4.6.1 Fracture Reactivation 

The reactivation of favourably oriented fractures is mechanically preferable to the creation of new 

fractures; when failure occurs, cohesion is lost. This lowers the Mohr-Coulomb failure envelope 

and field of stability, outlined in Figure 4.4, and allows rock to fail at lower shear and normal 

stress values. In Creighton, the rock mass in proximity to the excavation is assumed to be 

fractured, as inferred from both stress modelling and the distribution of seismicity. Fracture 

reactivation is thus a likely candidate for seismic emission. Zones subject to fracture reactivation 

can be mapped using Mohr-Coulomb failure conditions: 

 

n 

tan C 

(Equation 4.2) 

and the definitions of maximum normal and shear stresses, 

 

max 

1 

2 

 

and 

 

1 

3 

max 

1 

 

1 3 

. (Equations 4.3 and 4.4) 

2 

97

The ratio of maximum principal stresses can be expressed in terms of the angle of internal friction, 

 

 

3 

1 

1 

2 

2 

(tan 1) 

tan 

, (Equation 4.5) 

1 

2 

2 

(tan 1) 

tan 

when cohesion is zero (McKinnon, pers. comm., 2009; see Appendix F for derivation). This 

allows for zones of eligible fracture reactivation to be mapped regardless of fracture orientation. 

Minimum-to-maximum principal stress ratios computed for plastic and elastic models in UDEC 

are shown in Figure 4.22. Such figures allow fields of fault reactivation to be contoured as a 

function of the internal angle of friction (Fig. 4.23). This demonstrates that, based on the 

minimum-to-maximum principal stress ratio, there is a large area to the south of the excavation, 

extending to the Return Air Raise Shear Zone where cohesionless fractures in any orientation can 

be reactivated, even at high friction angles. This is modelled in both elastic and plastic models. 

Based on stress conditions, slip is possible even in the yield zone, though seismogenic slip is not 

expected. 

Figure 4.22: Ratio of minimum-to-maximum principal stress for (A) elastic model; (B) plastic model. 

98

Figure 4.23: Contoured domains of slip on cohesionless fractures at different angles of internal friction for 

(A) elastic model; (B) plastic model. 

4.6.2 Crack Initiation 

The initiation of new brittle failure is possible at stress levels much lower than the peak strength 

of the rock mass (Schultz, 1996). Crack initiation can be expected at levels from 0.3-0.5 σ UCS (Cai 

et al., 2004) and yield is modelled to occur between 0.4-0.5σ UCS for the Creighton granite 

(Diederichs, 2003). Fracture coalescence can occur from 0.7-0.8 σ UCS (Falmagne, 2001). Such 

thresholds have been applied to the 7400 Level using modelled stresses and the uniaxial 

compressive strength of footwall rocks to explore crack initiation as a mechanism for 

microseismicity in the Creighton Deep. The limits for fracture initiation and coalescence are 

shown in Figure 4.24. 

Crack initiation can also be described by differential stress, when its magnitude is a fraction of the 

peak strength. Differential stress threshold for the Lac du Bonnet granite is measured in the range 

of (σ 1 – σ 3 ) = 0.3 to 0.4σ UCS to (Falmagne, 2001). This threshold is used as an analogue to the 

Creighton granite. Differential stress plots outline zones of potential crack initiation (Fig. 4.24). 

99

Damage zones produced using maximum stress and differential stress outline similar areas of 

fracture initiation. Areas of active excavation during the 2006-2007 time period as well as a zone 

of high-stress between the Return Air Raise Shear Zone and Plum Shear Zone are identified as 

areas of possible fracture initiation under both maximum stress and differential conditions. This 

demonstrates that fracturing of intact rock is a possible mechanism for seismicity to the south of 

the excavation where seismicity is observed, but the crack coalescence threshold is not surpassed. 

Fracture contours identify the area south of the excavation as a region that is in a state of damage 

but not yield (Fig. 4.24). This is a lower state of degradation than was found in Chapter 3 using 

seismic source parameters, where the rock mass to the south of the excavation was hypothesized 

to be in post-peak conditions. 

Figure 4.24 shows that cracking is not possible immediately to the north and south of the 

excavation, based on the final state of models produced for Case 1 (Φ=30 o , C=0 MPa). This is 

because yielding has already occurred and high stress cannot be accommodated by the 

disintegrated rock mass in this state. UDEC code and routines can be found in Appendix E. 

100

Figure 4.24: Fracture initiation thresholds mapped using maximum and differential stress conditions. 

4.7 Modelling Summary and Discussion 

The distribution of stress on the 7400 Level in Creighton Mine is strongly dependent on both the 

excavation geometry and the strength of the discontinuities. UDEC models demonstrate that 

cohesion and the friction angle of the discontinuities modify the flow of stress around the 

excavation. Faults must have sufficiently low friction values for shear slip to occur. Under the 

current stress field, faults must have some residual friction as low values produced unrealistic 

stress distributions. 

Models demonstrate that stress is substantially reduced in a yield zone adjacent to an excavation. 

Tensile and shear failure associated with the yield zone is directly incurred by the presence of the 

excavation. Diederichs (2003) states that this is an area of tensile fracture accumulation and 

101

propagation as confining stresses are relaxed. Beyond this exists a damage zone where yielding 

occurs with some localization along failure planes. High stresses occur on the periphery of the 

yield zone as the rock transitions from a fractured rock mass into a stronger, more intact rock 

mass. This parallels the rock mass model of an inner yield zone, damage zone and outer intact 

zone as discussed in Chapter 3. 

When the faults are weaker than the rock mass, right-lateral slip is induced on the Plum Shear 

Zone and often on the Return Air Raise Shear Zone to the south of the excavation. Remote to the 

excavation, no slip occurs along these or other discontinuities. The deflection of stress around the 

excavation may act to enhance the normal stress, and thus the frictional resistance, along 

discontinuities remote from the excavation, preventing slip. Closer to the excavation maximum 

principal stresses are reduced but oriented at a low angle to the Plum Shear Zone, increasing the 

shear stress on the fault and instigating slip in both plastic and elastic models. This, however, 

occurs within the yield zone and may not contribute to seismogenic slip. 

4.7.1 Synthesis: Stress, Seismicity and Structure 

The relationship between structure and seismicity in the Creighton Deep is intimately linked to 

stress. The spatial distribution of seismicity closely corresponds to zones of high stress. A 

comparison of seismicity and stress is shown in Figure 4.25. This similar distribution supports the 

idea of the presence of a yield zone in proximity to the excavation where low stress and no 

seismicity occurs; a damage zone of high stress where dense seismicity occurs, and beyond this an 

intact zone where low to intermediate stress is associated with little seismicity, as discussed in 

Chapter 3. Both the distribution of stress and seismicity appear to be modified to align with the 

strike of the 118-System shear zones, but not within the shear zones themselves. The exception is 

102

seismic Cluster 1, which corresponds to an area of elevated modelled differential stress but with 

background levels of modelled maximum stress (Fig. 4.25). 

Geological evidence of degradation is difficult to observe in underground conditions due to 

limited access and enhanced support in proximity to the excavation. However, drilling supports 

this degradation process. Drill cores in proximity to the main excavation (in the proposed yield 

zone) are heavily fractured and highly degraded (Dave Andrews; pers. comm., 2009). The 

damage zone has already extended below the base of the mine at the 7940 ramp, which is also 

evident from drilling and excavation as the mine is progressively deepened (Dave Andrews; pers. 

comm., 2009). 

Slip along mine-scale shear zones has not been identified as a failure mechanism during seismic 

or stress analysis. Instead, slip along existing fractures and cracking of intact rock have been 

demonstrated to be plausible alternative mechanisms to fault slip. Mapping zones of fracture 

reactivation and crack initiation using modelled stresses suggests that existing fractures without 

cohesion may be reactivated and new cracks can form in zones of high stress. Though modelled 

stresses are not elevated enough to lead to fracture interaction and coalescence, clustering of 

seismic events signifies the onset of yield as the rock mass is seismically weakened, which 

supports observations made using seismic event parameters in Chapter 2. 

103

Figure 4.25: Comparison of stress and seismicity. (A) Distribution of seismicity on the 7400 Level; (B) 

highlighted areas of dense seismicity; (C) maximum stress distribution and (D) differential stress for 

comparison. Faults have C = 0 MPa and Ø= 35°. 

4.7.2 Model Limitations 

Mining is a three-dimensional process; blasting and material extraction occur on multiple levels 

simultaneously. Mining-induced stress on any given level is the result of stress flow around the 

excavation as well as contributions from mining above and below. Two-dimensional models thus 

are a simplification of the three-dimensional problem. 

Models of the 7400 Level suffer from this problem, limiting the comparison of stress on 

individual levels with seismicity. The westernmost cluster, (Cluster 1, as defined in Chapter 3) 

104

contains energetic events and is not wholly accounted for by stress models. In this area models 

show elevated differential stress as compared to background stress but lower maximum stress as 

compared to other seismically active areas. Influences external to the 7400 Level may play an 

important role in generating seismicity in this area. During the 2006-2007 time period, two 

orebodies may contribute to stress changes: the 461 Orebody, mined from 7680 to 7755 Level and 

the Plum Orebody, which is mined on levels above (Vale Inco, pers. comm., 2009). A threedimensional 

model incorporating these orebody geometries would allow for a more 

comprehensive analysis of stress distribution in the Deep. 

105

Chapter 5 

Conclusions and Recommendations 

5.1 Summary 

The goal of this study was to examine the relationship between the structures in the Creighton 

Deep and mining-induced seismicity. This was accomplished through geological investigations, 

seismic analysis and numerical modelling of stress. 

Geological investigations identified four principal systems of structures: the Footwall Shear Zone, 

E–W-striking shear zones, SW-striking shear zones (the 118 System) and splays between SWstriking 

shear zones. Numerical stress modelling demonstrates that these structures constitute 

weak zones within the rock mass and underground investigations indicate that such structures are 

healed. The Footwall Shear Zone and 1290 Shear Zone are laterally and vertically continuous but 

have little impact on stress or seismicity. SW-striking shear zones do not have a consistent 

composition and often do not correlate level-to-level. Small displacements were noted along 

younger fractures that cross-cut shear zones and foliation rather than along the shear zones 

themselves, further suggesting that shear zones are healed. 

Analysis of seismic events within the Creighton Deep did not reveal a relationship between 

structure and seismicity. Microseismic events do not spatially correspond to the mapped fault 

geometry. Furthermore, analysis of seismic event parameters does not reveal any spatial 

correlation to shear zones but does reveal areas of preferred seismic activity. Focal mechanisms 

of these microseismic events do not indicate any spatial correlation with structure. Consistency in 

focal plane solution axes for microseismic events, however, suggests that slip occurs on 

106

preferentially oriented fracture planes but fracture orientations do not conform to mine-scale shear 

zone orientations. Macroseismic event focal mechanisms are inconsistent and fault plane 

solutions do not have coherent nodal planes or pressure and tension axes. A stress inversion of P- 

and T-axes from microseismic events on the 7400 Level indicates that mine-scale stress 

orientations are consistent with far-field stresses. 

An anomalous cluster of microseismic and macroseismic events, referred to as Cluster 1 in this 

thesis, exhibits unusual seismic event parameter values and stress inversion results. Influences 

external to the 7400 Level, including mining of the Plum Orebody and 461 Orebody, may create a 

complex stress environment, complicating analysis of the 7400 Level. 

Numerical modelling of stress on the 7400 Level shows that stress flows around the excavation, 

forming a ring of high stress. In this two-dimensional analysis, there is little deflection in stress 

trajectories in proximity to faults. This suggests that faults are strong and brittle. High stresses 

align parallel to SW-striking structures to the south of the excavation, lowering stresses to the 

southwest. Comparison of modelling results with seismicity shows an agreement between areas 

of high stress and areas of dense seismicity, as well as between areas of low modelled stress and 

areas of little to no seismicity. Numerical models that allow for non-recoverable deformation 

show yielding around the excavation and along SW-striking shear zones and both elastic and 

plastic models demonstrate slip along the Plum Shear Zone and often along the Return Air Raise 

Shear Zone in proximity to the excavation, though this occurs where the rockmass has yielded. 

5.2 Conclusions 

Given that large-magnitude events require large slip surfaces, it would be expected that mine-scale 

shear zones would provide the area necessary to produce macroseismic events in the Creighton 

107

Deep. Little evidence, however, has been found in this thesis to support displacements along 

mine-scale discontinuities as a source of seismicity in the footwall region to the south of the 

excavation. Results indicate that seismicity in the Creighton Deep is the product of a degradation 

process. As stress flows around the excavation, zones of high stress are created that coincide with 

zones of preferential seismic activity. Shear zones slightly modify the stress field to the south of 

the excavation by realigning high stresses with the strike of major structures and reducing stress to 

the southwest of the excavation where little seismicity is observed. Shear zones in Creighton 

Deep thus only play a secondary role in the production of seismicity by modifying the stress state. 

Seismicity on mine levels in the Creighton Deep can be explained by the diffusion of rock mass 

degradation. Immediately to the north and south of the excavation, rock is heavily fractured and 

permanently strained in a yield zone. The rock mass in this zone cannot accommodate high stress 

and this stress is transferred to the peripheral damage zone. Little to no seismicity is recorded 

within the yield zone and this area is modelled as having yielded and as having low stress and low 

differential stress. 

The damage zone has been demonstrated to be an area of damage accumulation, where crack 

initiation and fracture reactivation are possible seismic sources. This zone contains the highest 

modelled stresses and hosts the densest seismic activity. It is recognized as a zone of increased 

seismic hazard. Rock is intact beyond the damage zone and little seismicity occurs remote to 

mine drifts. Stress levels in the damage zone are near background levels. 

Large events are often associated with structure, and in many instances fault slip is the source of 

high magnitude seismic events. While seismic and stress analyses conducted in this thesis have 

not revealed any significant relationship between mining-induced seismicity and structure, the 

108

methodologies employed are of value to other underground environments excavating in disturbed 

ground, and may show more positive results in cases where faults are geologically weak. 

5.3 Recommendations for Future Work 

Based on the results of this study, the following recommendations are made: 

 

Continued monitoring of seismic event parameters should be carried out in order to identify 

signs of further rock mass degradation. Extra caution should be given to the area identified as 

Cluster 1. This is identified as an area of increased hazard and continues to be a source of 

energetic events. Further studies of events in this area may help characterize and understand 

anomalous activity in this area. 

 

Additional triaxial sensors are recommended to improve location accuracy and to facilitate 

further seismic studies in the Creighton Deep. Denser spacing in key areas of interest may 

also facilitate studies. 

A comparison of fault plane solutions for microseismic events with joint fabric on the 7400 

Level is suggested as future work. A correlation with joint planes may explain the deviation 

of estimated fault plane orientations from mapped fault orientations. 

 

Moment tensor inversion for microseismic events is recommended to study the damage 

process and characterize seismicity. Mechanisms such as crack dilation and closure could be 

identified using this method. Moment tensor inversion may also be a suitable method for 

studying events in Cluster 1. 

 

Further analysis of macroseismic events is recommended once the triaxial strong ground 

motion system is calibrated. Waveforms recorded by the calibrated triaxial system will allow 

109

for the calculation of seismic event parameters, which will aid in characterizing large events in 

the Creighton Deep. 

 

Mine personnel should recognize the role of faults in influencing the flow of stress when 

monitoring established levels. 

 

Three-dimensional models are recommended in order to gain insight into stress migration 

from sources external to the 7400 Level. The 461 Orebody and Plum Orebody seem to have 

an effect on stress distribution and have a large impact on seismicity in Cluster 1. 

 

Lastly, diligent structural mapping and shear characterization is highly recommended to 

further develop and refine the existing structural model. Knowledge of geological 

environment is essential to understand the response of the rock mass to mining. It is 

recommended that structures encountered during excavation be thoroughly described and 

documented before applying shotcrete or support that inhibits future analysis. Descriptions 

should include dimensions of high strain zones and damage zones as well as incidences of 

fault gauge, slickenlines, brittle failure and brittle kinematic indicators. 

110

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116

Appendix A 

Geological Maps and Sample Locations 

A.1 Site Locations 

Site locations, samples and thin sections are summarized in Table A1. 

 

 

 

 

A denotes cut along lineation, perpendicular to foliation 

B denotes cut perpendicular to lineation and foliation 

C denotes cut along slickenlines, perpendicular to foliation 

No assigned letter indicates cut along lineation, perpendicular to foliation (A) 

Table A1: Summary of site visit locations, oriented samples and thin sections 

Location Level Feature 

Oriented 

Sample 

Thin Section 

29-1 7680 6730 Sill -- -- 

29-2 7810 Isoclinally folded breccia -- -- 

29-3 7810 Isoclinally folded breccia -- -- 

02-1 7940 Fresh Air Raise-Type Shear Zone Yes 02-1 

02-2 7940 Fresh Air Raise-Type Shear Zone Yes (02-2) 02-2A, 02-2B, 02-2L 

02-3 7400 Footwall Shear Zone Yes (02-3) 02-3 

02-4 7400 Footwall Shear Zone Yes (02-4) 02-4 

02-5 7400 RAR Shear Zone Yes (02-5) 02-5A 

02-6 7400 Grizzly Splay Shear Zone Yes (02-6) 02-6A, 02-6B 

03-1 7940 Fresh Air Raise-Type Shear Zone Yes -- 

03-2 7530 Footwall Shear Zone -- -- 

03-3 7530 Minor shear along dyke Not oriented -- 

03-4 7530 Cracked shotcrete along RAR Shear Zone -- -- 

04-1 7680 Return Air Raise Shear Zone -- -- 

04-2A, B 7680 Near projected Northwest Shear Zone -- -- 

04-3 7680 Near projected Northwest Shear Zone -- -- 

04-5 7680 Projected Plum Shear Zone location -- -- 

04-6 7680 Shear zone parallel to Footwall Shear Zone Not oriented 04-6 

04-7 7680 Footwall Shear Zone Yes 04-7A, 04-7B 

117

05-1A-D 7810 400-East Shear Zone and 1290 Shear Zone Yes 05-1D A, 05-1D B, 05- 

1D A1, 05-1D C 

05-2A-J 7810 Isoclinally folded breccia -- -- 

05-3 7810 -- -- 

05-4 7810 Minor shear zone -- -- 

05-5 7810 Veins in projected Plum Shear location -- -- 

05-6 7810 Face exposure -- -- 

05-7 7810 Face exposure -- -- 

09-1 7680 Footwall Shear Zone (same as 04-7) Not oriented -- 

09-2 7400 Grizzly Splay Shear Zone (same as 02-6) Yes 02-6A, 02-6B 

09-3 7200 Persistent joints marked as ‘Shear Zone’ -- -- 

09-4 7200 FAR Shear Zone Yes 09-4A, 09-4B 

09-5 7200 Projected Plum Shear Zone location -- -- 

09-6 7200 Projected 1290 Shear location -- -- 

09-7 7200 Strained but cohesive granite and gabbro -- -- 

10-2 6600 Footwall Shear Zone Yes 10-2A, 10-2B 

10-3 6600 Deformed quartz boudins -- -- 

10-4 6600 Localized failure and overbreak -- -- 

10-5 7000 Projected Plum Shear location -- -- 

10-6 7000 Near Projected Plum Shear location Yes 10-6A 

10-7 7810 400-East Shear Zone (same as 05-1) -- -- 

11-1 7680 Large parallel quartz veins -- -- 

11-2 7680 Folded dykelet (?) -- -- 

11-3 7680 Near projected NW shear Yes -- 

11-4 7680 RAR Shear Zone Yes 12-4A 

11-5 7680 Veins and brittle fractures -- -- 

11-6 7680 RAR Shear Zone -- -- 

11-7 7680 Near projected NW shear -- -- 

16-1 7810 Minor shear in Face -- -- 

17-1 7400 FAR Shear Zone Yes 17-1A, 17-1B 

17-2 7400 Minor shear at lithological contact -- -- 

17-3 7150 Pinched out vein near projected 402 Shear 

Zone location 

118 

-- -- 

17-4 7150 Pinched out vein -- -- 

17-5 6900 Zone of high strain -- -- 

18-1 6400 1290 Shear Zone Yes 18-1

A.2 Level Plans with Sample Locations 

Figure A1: 7000 Level, modified form Vale Inco. RAR = Return Air Raise; FAR = Fresh Air Raise. 

119

Figure A2: 7200 Level, modified form Vale Inco. NW= Northwest; RAR = Return Air Raise; FAR = Fresh Air Raise. 

120


121


122


123

Figure A6: 7810 Level, modified form Vale Inco. RAR = Return Air Raise; FAR = Fresh Air Raise. 

124

Figure A7: 7940 Ramp, modified from Vale Inco. FAR = Fresh Air Raise. 

125

Appendix B 

Seismic Event Parameters 

B.1 Event Population Statistics for the Creighton Deep 

Table B1: Summary Statistics for microseismic, macroseismic and blast events below 7000 feet with 

location errors less than 30 feet. 

MICROSEISMIC 

EVENTS Error Ns Nu uMag Nt tMag 

Mom. 

Mag. 

LOG 

M 

LOG 

E Es/Ep 

Mean 18.31 21.91 14.95 -2.70 5.23 -1.85 -1.04 7.87 2.51 8.62 

Standard Error 0.05 0.07 0.04 0.01 0.02 0.01 0.00 0.01 0.02 0.06 

Median 18.00 21.00 15.00 -2.70 5.00 -1.90 -1.10 7.64 2.30 7.60 

Mode 16.00 20.00 15.00 -2.80 6.00 -2.10 -1.30 7.01 2.03 5.50 

Standard Dev. 4.80 5.89 3.83 0.54 1.49 0.70 0.44 0.84 1.61 5.14 

Sample Variance 23.01 34.68 14.65 0.29 2.23 0.49 0.19 0.70 2.58 26.47 

Kurtosis -0.28 -0.16 -0.16 0.97 -0.49 8.83 82.21 0.21 -0.45 32.91 

Skewness 0.38 0.37 0.05 0.57 -0.05 -0.10 -3.34 0.94 0.51 3.61 

Range 24.00 35.00 27.00 4.90 9.00 11.40 10.70 4.18 8.27 92.20 

Minimum 6.00 8.00 3.00 -4.60 0.00 -9.90 -9.90 6.49 -0.63 0.10 

Maximum 30.00 43.00 30.00 0.30 9.00 1.50 0.80 10.68 7.64 92.30 

Count 8066 8066 8066 8066 8066 8066 8066 8061 8061 8061 

MACROSEISMIC 

EVENTS Error Ns Nu uMag Nt tMag 

Es/Ep 

Mean 19.48 33.47 14.96 -1.17 6.70 -0.08 0.12 9.69 5.73 17.17 


Median 18.00 34.00 15.00 -1.20 7.00 0.00 0.10 9.74 5.84 13.55 

Mode 18.00 34.00 19.00 -1.10 6.00 0.50 0.20 9.55 6.53 8.40 

Standard Dev. 4.07 4.24 4.48 0.47 1.27 0.63 0.27 0.46 1.03 14.84 


Kurtosis 0.05 -0.38 -0.58 0.53 0.76 -0.28 -0.34 -0.31 -0.28 9.46 

Skewness 0.70 -0.26 -0.03 0.21 -0.50 -0.05 0.10 -0.40 -0.53 2.69 

Range 18.00 20.00 20.00 2.70 6.00 3.10 1.20 2.10 4.55 91.20 

Minimum 12.00 23.00 5.00 -2.40 3.00 -1.60 -0.40 8.58 3.09 1.10 

Maximum 30.00 43.00 25.00 0.30 9.00 1.50 0.80 10.68 7.64 92.30 

Count 98 98 98 98 98 98 98 98 98 98 

BLASTS Error Ns Nu uMag Nt tMag 

Mean 21.16 25.79 16.44 -1.69 5.36 -1.07 -0.38 9.07 4.54 5.44 


Median 21.00 27.00 17.00 -1.60 6.00 -1.00 -0.30 9.30 5.05 4.30 

Mode 18.00 30.00 19.00 -1.50 6.00 -1.00 -0.20 8.14 5.17 2.30 

Standard Dev. 4.50 6.95 5.33 0.66 1.19 0.66 0.45 0.89 1.68 3.60 


Kurtosis -0.46 -0.03 0.18 0.32 0.24 0.74 0.12 -0.17 -0.20 1.48 

Skewness -0.09 -0.44 -0.29 -0.45 -0.45 -0.68 -0.84 -0.88 -0.80 1.38 

Range 23.00 36.00 27.00 3.50 6.00 3.50 1.90 3.66 7.29 16.50 

Minimum 7.00 8.00 3.00 -3.60 2.00 -3.20 -1.50 6.86 0.15 0.60 

Maximum 30.00 44.00 30.00 -0.10 8.00 0.30 0.40 10.51 7.43 17.10 

Count 145 145 145 145 145 145 145 145 145 145 

126 

Mom. 

Mag. 

Mom. 

Mag. 

LOG 

M 

LOG 

M 

LOG 

E 

LOG 

E 

Es/Ep

MICROSEISMIC 

EVENTS 

Source 

Radius 

Asp. 

Radius 

LOG 

Static 

SD 

LOG 

App. 

Stress 

LOG 

Dynamic 

SD. 

LOG 

Max. 

Displ. 

LOG 

Peak 

Vel. 

LOG 

Peak 

Acc. 

Mean 2.89 0.72 6.27 5.20 6.81 -3.82 -1.62 5.71 

Standard Error 0.01 0.00 0.01 0.01 0.01 0.01 0.01 0.01 

Median 2.77 0.62 6.24 5.16 6.70 -3.94 -1.74 5.60 

Mode 2.46 1.06 6.00 5.03 7.03 -3.92 -1.95 5.09 

Standard Deviation 0.75 0.36 0.64 0.86 0.58 0.69 0.69 0.58 

Sample Variance 0.56 0.13 0.41 0.74 0.34 0.47 0.47 0.34 

Kurtosis 1.26 6.65 -0.47 -0.75 0.14 -0.05 -0.05 0.14 

Skewness 0.87 2.10 0.12 0.11 0.78 0.69 0.69 0.78 

Range 7.92 3.52 3.83 4.75 3.39 3.92 3.92 3.39 

Minimum 1.08 0.23 4.55 3.08 5.40 -5.44 -3.24 4.30 

Maximum 9.00 3.75 8.38 7.83 8.79 -1.52 0.69 7.69 

Count 8061 8061 8061 8061 8061 8061 8061 8061 

REPORTABLE 

EVENTS 

Source 

Radius 

Asp. 

Radius 

LOG 

Static 

SD 

LOG 

App. 

Stress 

LOG 

Dynamic 

SD. 

LOG 

Max. 

Displ. 

LOG 

Peak 

Vel. 

LOG 

Peak 

Acc. 

Mean 4.38 1.69 7.37 6.60 7.79 -2.43 -0.23 6.69 


Median 4.50 1.65 7.44 6.61 7.85 -2.34 -0.13 6.75 

Mode 4.13 1.68 7.89 6.30 8.26 -2.87 -0.67 7.16 



Kurtosis -0.05 1.37 -0.49 -0.23 -0.04 -0.45 -0.45 -0.05 

Skewness -0.56 0.85 -0.40 -0.38 -0.65 -0.39 -0.39 -0.65 

Range 2.85 2.50 2.13 2.81 2.12 1.90 1.90 2.12 

Minimum 2.65 0.67 6.25 5.02 6.67 -3.42 -1.21 5.57 

Maximum 5.50 3.17 8.38 7.83 8.79 -1.52 0.69 7.69 

Count 98 98 98 98 98 98 98 98 

BLASTS 

Source 

Radius 

Asp. 

Radius 

LOG 

Static 

SD 

LOG 

App. 

Stress 

LOG 

Dynamic 

SD. 

LOG 

Max. 

Displ. 

LOG 

Peak 

Vel. 

LOG 

Peak 

Acc. 

Mean 4.13 1.94 6.92 6.03 7.21 -3.04 -0.84 6.11 


Median 4.33 1.88 7.03 6.29 7.26 -2.90 -0.69 6.15 

Mode 4.94 3.14 6.08 6.48 6.68 -3.23 -0.51 5.58 



Kurtosis -0.80 -0.94 -0.26 0.00 -0.83 -0.04 -0.04 -0.83 

Skewness -0.36 0.29 -0.61 -0.70 -0.06 -0.54 -0.53 -0.06 

Range 4.63 4.01 3.07 4.38 2.72 3.36 3.37 2.72 

Minimum 1.63 0.33 5.02 3.47 5.74 -4.99 -2.79 4.64 

Maximum 6.26 4.34 8.09 7.84 8.46 -1.63 0.58 7.36 

Count 145 145 145 145 145 145 145 145 

127

Log E 

10 

8 

6 

4 

Energy-Moment Relataion 

LogE = 2.13 LogM - 14.90 

LogE = 1.84 LogM - 12.17 

LogE = 1.75 LogM - 11.28 

Events 

Blasts 

Reportable 

Linear (Reportable) 

Linear (Blasts) 

Linear (Events) 

2 

0 

-2 

0 2 4 6 8 10 12 

Log M 

Figure B1: Energy-Moment relation showing distribution of events, blasts and large magnitude events. 

Well-located events (

2006 Event Frequency with Depth 

6000 

5000 

Frequency 

4000 

3000 

2000 

1000 

0 

3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 

Depth (feet) 

Figure B3: Events within Creighton Mine increase with Depth. This is shown in this event frequency 

histogram. This trend is noted over many years, though some increase on lower levels reflects level 

development. 

Distribution of Recorded Events (2006 Data, 

Below 7300 ft.) 

123 

979 

e 

r 

b 

9317 

Figure B4: Events within the Creighton Deep study area consists of mostly microseismic events (89.4%), 

blasts (9.4%) and few macroseismic events (1.2%) 

129

Frequency of 2006 Events by Month 

1600 

1400 

1200 

Frequency 

1000 

800 

600 

400 

200 

0 

Jan 

Feb 

Mar 

Apr 

May 

Jun 

Jul 

Aug 

Sep 

Oct 

Nov 

Dec 

Month 

Figure B5: Event frequency by month reveals some seasonality to events. Higher event rates occur in 

November to January, while low rates occur after a late summer shut-down. 

Event frequency by hour, 2006 events 

700 

600 

500 

Frequency 

400 

300 

200 

100 

0 

1 3 5 7 9 11 13 15 17 19 21 23 

Time (Hour) 

Figure B6: Event Frequency is plotted by hour. High event rates in early morning hours reflect blasting 

schedules for the Creighton Deep. 

130

B.2 Spatial Distribution of Seismic Event Parameters for the 7400 Level 

Figure B7: Events between Jan 1, 2006 and Dec 31 2007 pertaining to the 7400 Level, coloured by 

magnitude. 

Figure B8: Events between Jan 1, 2006 and Dec 31 2007 pertaining to the 7400 Level, coloured by the 

number of phones used in recording, a relative measure of magnitude. 

131


Seismic Energy (Log scale used). 


Seismic Moment (Log scale used). 

132


dynamic stress drop (Log scale used). 

Figure B12: Events between Jan 1, 2006 and Dec 31 2007 pertaining to the 7400 Level, coloured by static 

stress drop (Log scale used). 

133

Figure B13: Events between Jan 1, 2006 and Dec 31 2007 pertaining to the 7400 Level, coloured by static 

stress drop (Log scale used). 

Figure B14: Events between Jan 1, 2006 and Dec 31 2007 pertaining to the 7400 Level, coloured by peak 

particle velocity (Log scale used). 

134

Figure B15: Events between Jan 1, 2006 and Dec 31 2007 pertaining to the 7400 Level, coloured by peak 

particle acceleration (Log scale used). 


maximum particle displacement (Log scale used). 

135


source radius 


asperity radius 

136


location error. Events that locate outside the network to the north have a greater location error. 

137

B.3 Cluster Statistics 

Table B2: Summary Statistics for microseismic event clusters about the 7400 Level with location errors 

less than 30 feet. 

Cluster 1 Error Ns Nu uMag Nt tMag 

Mom. 

Mag. 

LOG 

M 

LOG 

E 

Es/Ep 

Mean 17.06 21.89 15.57 -2.67 6.32 -1.61 -1.11 7.79 3.28 8.89 


Median 17.00 22.00 16.00 -2.70 6.00 -1.70 -1.20 7.67 3.20 7.70 

Mode 18.00 24.00 17.00 -2.80 6.00 -2.00 -1.20 7.49 3.11 6.30 

Standard Dev. 4.01 3.72 3.26 0.48 1.11 0.50 0.30 0.57 0.97 5.04 


Kurtosis 0.13 0.06 0.13 0.47 -0.45 1.20 2.01 1.29 0.74 29.63 

Skewness 0.54 -0.39 -0.34 0.54 -0.27 0.92 0.99 1.00 0.49 3.85 

Range 21.00 22.00 20.00 3.00 5.00 3.00 2.00 3.74 6.34 62.30 

Minimum 9.00 9.00 5.00 -3.90 3.00 -2.70 -1.90 6.19 0.37 2.60 

Maximum 30.00 31.00 25.00 -0.90 8.00 0.30 0.10 9.93 6.71 64.90 

Count 619 619 619 619 619 619 619 619 619 619 


Mom. 

Mag. 

LOG 

M 

LOG 

E 

Es/Ep 

Mean 15.88 22.96 15.04 -2.92 6.46 -2.04 -1.28 7.37 1.73 7.52 


Median 15.00 23.00 15.00 -3.00 7.00 -2.20 -1.30 7.26 1.58 6.70 

Mode 16.00 19.00 17.00 -2.80 8.00 -2.40 -1.50 7.23 1.38 4.70 

Standard Dev. 3.67 5.19 3.05 0.48 1.39 0.62 0.32 0.57 1.18 4.83 


Kurtosis 1.83 -0.38 0.26 1.20 -0.70 0.05 1.23 1.14 -0.34 120.14 

Skewness 1.11 0.09 -0.29 0.79 -0.50 0.78 0.75 0.73 0.55 9.00 

Range 21.00 27.00 18.00 3.30 5.00 3.10 1.90 3.47 5.21 71.40 

Minimum 9.00 10.00 5.00 -4.10 3.00 -3.10 -2.10 5.85 -0.19 2.40 

Maximum 30.00 37.00 23.00 -0.80 8.00 0.00 -0.20 9.32 5.02 73.80 

Count 297 297 297 297 297 297 297 297 297 297 


138 

Mom. 

Mag. 

LOG 

M 

LOG 

E 

Es/Ep 

Mean 14.78 21.55 14.13 -3.10 5.84 -2.22 -1.37 7.23 1.31 9.42 


Median 15.00 20.50 14.00 -3.10 6.00 -2.35 -1.40 7.12 0.98 8.60 

Mode 15.00 20.00 14.00 -3.10 5.00 -2.80 -1.50 7.01 0.31 8.60 

Standard Dev. 3.60 5.67 3.29 0.49 1.44 0.65 0.38 0.68 1.22 4.72 


Kurtosis 0.75 -0.29 -0.30 -0.22 -0.43 0.71 2.34 1.11 0.40 19.43 

Skewness 0.46 0.52 -0.16 0.24 -0.22 0.97 0.84 0.68 0.94 3.24 

Range 22.00 28.00 17.00 2.60 6.00 3.70 2.40 3.94 6.13 44.30 

Minimum 6.00 9.00 5.00 -4.20 2.00 -3.50 -2.20 5.73 -0.57 2.00 

Maximum 28.00 37.00 22.00 -1.60 8.00 0.20 0.20 9.67 5.56 46.30 

Count 220 220 220 220 220 220 220 220 220 220

Cluster 1 

Source 

Radius 

Asp. 

Radius 

LOG 

Static 

SD 

LOG 

App. 

Stress 

LOG 

Dynamic 

SD. 

LOG 

Max. 

Displ. 

LOG 

Peak 

Vel. 

LOG 

Peak 

Acc. 

Mean 2.10 0.60 6.84 6.05 7.12 -3.56 -1.36 6.02 


Median 2.12 0.57 6.85 6.09 7.09 -3.59 -1.39 5.99 

Mode 2.03 0.53 7.01 6.24 7.01 -3.92 -1.72 5.98 



Kurtosis 0.49 2.94 0.67 1.35 0.25 0.68 0.69 0.24 

Skewness -0.32 1.40 -0.28 -0.57 0.57 0.67 0.67 0.57 

Range 3.14 1.23 2.47 3.71 2.28 2.81 2.81 2.28 

Minimum 0.73 0.30 5.39 3.79 6.19 -4.67 -2.47 5.09 

Maximum 3.87 1.53 7.86 7.51 8.47 -1.87 0.34 7.37 

Count 619 619 619 619 619 619 619 619 

Cluster 2 

Source 

Radius 

Asp. 

Radius 

LOG 

Static 

SD 

LOG 

App. 

Stress 

LOG 

Dynamic 

SD. 

LOG 

Max. 

Displ. 

LOG 

Peak 

Vel. 

LOG 

Peak 

Acc. 

Mean 2.24 0.59 6.11 4.92 6.50 -4.21 -2.01 5.40 


Median 2.34 0.55 6.14 4.93 6.43 -4.30 -2.10 5.33 

Mode 1.99 0.45 6.14 4.50 6.12 -4.45 -1.97 5.02 



Kurtosis -0.23 1.02 -0.45 -0.79 -0.13 -0.11 -0.11 -0.13 

Skewness -0.60 1.00 0.08 -0.03 0.64 0.68 0.68 0.65 

Range 3.19 1.13 2.83 3.39 1.99 2.29 2.29 1.99 

Minimum 0.70 0.25 5.05 3.52 5.82 -5.03 -2.83 4.72 

Maximum 3.89 1.38 7.88 6.91 7.80 -2.74 -0.53 6.70 

Count 297 297 297 297 297 297 297 297 

Cluster 3 

Source 

Radius 

Asp. 

Radius 

LOG 

Static 

SD 

LOG 

App. 

Stress 

LOG 

Dynamic 

SD. 

LOG 

Max. 

Displ. 

LOG 

Peak 

Vel. 

LOG 

Peak 

Acc. 

Mean 2.55 0.49 5.86 4.64 6.49 -4.30 -2.09 5.39 


Median 2.66 0.45 5.84 4.58 6.40 -4.46 -2.26 5.30 

Mode 2.46 0.38 5.35 5.31 6.10 -4.53 -2.47 5.00 

Standard Dev. 1.03 0.16 0.63 0.76 0.42 0.53 0.53 0.42 


Kurtosis -0.74 3.23 -0.83 -0.93 -0.07 0.15 0.15 -0.08 

Skewness -0.35 1.54 0.18 0.22 0.71 0.86 0.86 0.71 

Range 3.96 0.95 2.70 3.37 2.15 2.68 2.68 2.15 

Minimum 0.66 0.26 4.66 3.08 5.66 -5.28 -3.07 4.56 

Maximum 4.62 1.21 7.36 6.45 7.81 -2.60 -0.39 6.71 

Count 220 220 220 220 220 220 220 220 

139

B.4 Temporal Distribution of Seismic Event Parameters 

Events belonging to Clusters 1, 2 and 3, as identified in Chapter 3 are plotted to assess temporal 

variation. Events are shown in grey; a moving average of 50 events is shown in black. Events are as 

labeled. Bottom axis represents local time. 

Parameter units are summarized here: 

Seismic moment, Nm 

Energy, J 

Source radius, m 

Asperity radius, m 

Static stress drop, Pa 

Apparent stress drop, Pa 

Dynamic Stress drop, Pa 

Maximum displacement (m) 

Peak velocity, m/s 

Peak acceleration, m/s 2 

B.4.1 Temporal Distribution of Cluster 1 Events 


0.5 

0.0 

-0.5 

-1.0 

-1.5 

-2.0 

04/01/2006 

04/03/2006 

04/05/2006 

04/07/2006 

04/09/2006 

04/11/2006 

04/01/2007 

04/03/2007 

04/05/2007 

04/07/2007 

04/09/2007 

04/11/2007 

140

Seismic Moment 

10.0 

9.5 

9.0 

8.5 

8.0 

7.5 

7.0 

6.5 

6.0 

04/01/2006 

04/03/2006 

04/05/2006 

04/07/2006 

04/09/2006 

04/11/2006 

04/01/2007 

04/03/2007 

04/05/2007 

04/07/2007 

04/09/2007 

04/11/2007 

141

142 

Energy 

0.0 

1.0 

2.0 

3.0 

4.0 

5.0 

6.0 

7.0 

8.0 

04/01/2006 

04/02/2006 

04/03/2006 

04/04/2006 

04/05/2006 

04/06/2006 

04/07/2006 

04/08/2006 

04/09/2006 

04/10/2006 

04/11/2006 

04/12/2006 

04/01/2007 

04/02/2007 

04/03/2007 

04/04/2007 

04/05/2007 

04/06/2007 

04/07/2007 

04/08/2007 

04/09/2007 

04/10/2007 

04/11/2007 

04/12/2007 

Apparent Stress 

3.5 

4.0 

4.5 

5.0 

5.5 

6.0 

6.5 

7.0 

7.5 

04/01/2006 

04/02/2006 

04/03/2006 

04/04/2006 

04/05/2006 

04/06/2006 

04/07/2006 

04/08/2006 

04/09/2006 

04/10/2006 

04/11/2006 

04/12/2006 

04/01/2007 

04/02/2007 

04/03/2007 

04/04/2007 

04/05/2007 

04/06/2007 

04/07/2007 

04/08/2007 

04/09/2007 

04/10/2007 

04/11/2007 

04/12/2007 

Dynamic Stress Drop 

6.0 

6.5 

7.0 

7.5 

8.0 

8.5 

04/01/2006 

04/02/2006 

04/03/2006 

04/04/2006 

04/05/2006 

04/06/2006 

04/07/2006 

04/08/2006 

04/09/2006 

04/10/2006 

04/11/2006 

04/12/2006 

04/01/2007 

04/02/2007 

04/03/2007 

04/04/2007 

04/05/2007 

04/06/2007 

04/07/2007 

04/08/2007 

04/09/2007 

04/10/2007 

04/11/2007 

04/12/2007

143 

Peak Velocity Parameter 

-2.5 

-2.0 

-1.5 

-1.0 

-0.5 

0.0 

0.5 

04/01/2006 

04/03/2006 

04/05/2006 

04/07/2006 

04/09/2006 

04/11/2006 

04/01/2007 

04/03/2007 

04/05/2007 

04/07/2007 

04/09/2007 

04/11/2007 

Es/Ep 

0 

5 

10 

15 

20 

25 

30 

35 

40 

04/01/2006 

04/03/2006 

04/05/2006 

04/07/2006 

04/09/2006 

04/11/2006 

04/01/2007 

04/03/2007 

04/05/2007 

04/07/2007 

04/09/2007 

04/11/2007 

Source Radius 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

4.0 

04/01/2006 

04/02/2006 

04/03/2006 

04/04/2006 

04/05/2006 

04/06/2006 

04/07/2006 

04/08/2006 

04/09/2006 

04/10/2006 

04/11/2006 

04/12/2006 

04/01/2007 

04/02/2007 

04/03/2007 

04/04/2007 

04/05/2007 

04/06/2007 

04/07/2007 

04/08/2007 

04/09/2007 

04/10/2007 

04/11/2007 

04/12/2007

144 

Static Stress Drop 

5.0 

5.5 

6.0 

6.5 

7.0 

7.5 

8.0 

04/01/2006 

04/02/2006 

04/03/2006 

04/04/2006 

04/05/2006 

04/06/2006 

04/07/2006 

04/08/2006 

04/09/2006 

04/10/2006 

04/11/2006 

04/12/2006 

04/01/2007 

04/02/2007 

04/03/2007 

04/04/2007 

04/05/2007 

04/06/2007 

04/07/2007 

04/08/2007 

04/09/2007 

04/10/2007 

04/11/2007 

04/12/2007 

Complexity (DySD:StSD) 

0.0 

1.0 

2.0 

3.0 

4.0 

5.0 

6.0 

7.0 

8.0 

9.0 

10.0 

04/01/2006 

04/03/2006 

04/05/2006 

04/07/2006 

04/09/2006 

04/11/2006 

04/01/2007 

04/03/2007 

04/05/2007 

04/07/2007 

04/09/2007 

04/11/2007



0.0 

-0.5 

-1.0 

-1.5 

-2.0 

-2.5 

02/01/2006 

02/03/2006 

02/05/2006 

02/07/2006 

02/09/2006 

02/11/2006 

02/01/2007 

02/03/2007 

02/05/2007 

02/07/2007 

02/09/2007 

02/11/2007 


9.5 

9.0 

8.5 

8.0 

7.5 

7.0 

6.5 

6.0 

5.5 

02/01/2006 

02/03/2006 

02/05/2006 

02/07/2006 

02/09/2006 

02/11/2006 

02/01/2007 

02/03/2007 

02/05/2007 

02/07/2007 

02/09/2007 

02/11/2007 

145

146 

Energy 

-1.0 

0.0 

1.0 

2.0 

3.0 

4.0 

5.0 

6.0 

02/01/2006 

02/03/2006 

02/05/2006 

02/07/2006 

02/09/2006 

02/11/2006 

02/01/2007 

02/03/2007 

02/05/2007 

02/07/2007 

02/09/2007 

02/11/2007 

Es/Ep 

0 

5 

10 

15 

20 

25 

02/01/2006 

02/03/2006 

02/05/2006 

02/07/2006 

02/09/2006 

02/11/2006 

02/01/2007 

02/03/2007 

02/05/2007 

02/07/2007 

02/09/2007 

02/11/2007 

Source Radius 

0.0 

1.0 

2.0 

3.0 

4.0 

5.0 

02/01/2006 

02/03/2006 

02/05/2006 

02/07/2006 

02/09/2006 

02/11/2006 

02/01/2007 

02/03/2007 

02/05/2007 

02/07/2007 

02/09/2007 

02/11/2007

147 


5.0 

5.5 

6.0 

6.5 

7.0 

7.5 

8.0 

02/01/2006 

02/03/2006 

02/05/2006 

02/07/2006 

02/09/2006 

02/11/2006 

02/01/2007 

02/03/2007 

02/05/2007 

02/07/2007 

02/09/2007 

02/11/2007 


3.0 

3.5 

4.0 

4.5 

5.0 

5.5 

6.0 

6.5 

7.0 

02/01/2006 

02/03/2006 

02/05/2006 

02/07/2006 

02/09/2006 

02/11/2006 

02/01/2007 

02/03/2007 

02/05/2007 

02/07/2007 

02/09/2007 

02/11/2007 


5.0 

5.5 

6.0 

6.5 

7.0 

7.5 

8.0 

02/01/2006 

02/03/2006 

02/05/2006 

02/07/2006 

02/09/2006 

02/11/2006 

02/01/2007 

02/03/2007 

02/05/2007 

02/07/2007 

02/09/2007 

02/11/2007


0.30 

0.25 

0.20 

0.15 

0.10 

0.05 

0.00 

02/01/2006 

02/03/2006 

02/05/2006 

02/07/2006 

02/09/2006 

02/11/2006 

02/01/2007 

02/03/2007 

02/05/2007 

02/07/2007 

02/09/2007 

02/11/2007 

Complexity (DySD:StSD) 

12.0 

10.0 

8.0 

6.0 

4.0 

2.0 

0.0 

02/01/2006 

02/03/2006 

02/05/2006 

02/07/2006 

02/09/2006 

02/11/2006 

02/01/2007 

02/03/2007 

02/05/2007 

02/07/2007 

02/09/2007 

02/11/2007 

148



0.5 

0.0 

-0.5 

-1.0 

-1.5 

-2.0 

-2.5 

17/01/2006 

17/03/2006 

17/05/2006 

17/07/2006 

17/09/2006 

17/11/2006 

17/01/2007 

17/03/2007 

17/05/2007 

17/07/2007 

17/09/2007 

17/11/2007 


10.0 

9.0 

8.0 

7.0 

6.0 

5.0 

17/01/2006 

17/03/2006 

17/05/2006 

17/07/2006 

17/09/2006 

17/11/2006 

17/01/2007 

17/03/2007 

17/05/2007 

17/07/2007 

17/09/2007 

17/11/2007 

149

150 

Energy 

-1.0 

0.0 

1.0 

2.0 

3.0 

4.0 

5.0 

6.0 

17/01/2006 

17/03/2006 

17/05/2006 

17/07/2006 

17/09/2006 

17/11/2006 

17/01/2007 

17/03/2007 

17/05/2007 

17/07/2007 

17/09/2007 

17/11/2007 

Es/Ep 

0 

5 

10 

15 

20 

25 

30 

17/01/2006 

17/03/2006 

17/05/2006 

17/07/2006 

17/09/2006 

17/11/2006 

17/01/2007 

17/03/2007 

17/05/2007 

17/07/2007 

17/09/2007 

17/11/2007 

Source Radius 

0.0 

1.0 

2.0 

3.0 

4.0 

5.0 

17/01/2006 

17/03/2006 

17/05/2006 

17/07/2006 

17/09/2006 

17/11/2006 

17/01/2007 

17/03/2007 

17/05/2007 

17/07/2007 

17/09/2007 

17/11/2007

151 


4.0 

4.5 

5.0 

5.5 

6.0 

6.5 

7.0 

7.5 

8.0 

17/01/2006 

17/03/2006 

17/05/2006 

17/07/2006 

17/09/2006 

17/11/2006 

17/01/2007 

17/03/2007 

17/05/2007 

17/07/2007 

17/09/2007 

17/11/2007 


3.0 

3.5 

4.0 

4.5 

5.0 

5.5 

6.0 

6.5 

7.0 

17/01/2006 

17/03/2006 

17/05/2006 

17/07/2006 

17/09/2006 

17/11/2006 

17/01/2007 

17/03/2007 

17/05/2007 

17/07/2007 

17/09/2007 

17/11/2007 


5.0 

5.5 

6.0 

6.5 

7.0 

7.5 

8.0 

17/01/2006 

17/03/2006 

17/05/2006 

17/07/2006 

17/09/2006 

17/11/2006 

17/01/2007 

17/03/2007 

17/05/2007 

17/07/2007 

17/09/2007 

17/11/2007


0.0 

-0.5 

-1.0 

-1.5 

-2.0 

-2.5 

-3.0 

-3.5 

17/01/2006 

17/03/2006 

17/05/2006 

17/07/2006 

17/09/2006 

17/11/2006 

17/01/2007 

17/03/2007 

17/05/2007 

17/07/2007 

17/09/2007 

17/11/2007 

Com pexity (DySD:StSD) 

30.0 

25.0 

20.0 

15.0 

10.0 

5.0 

0.0 

17/01/2006 

17/03/2006 

17/05/2006 

17/07/2006 

17/09/2006 

17/11/2006 

17/01/2007 

17/03/2007 

17/05/2007 

17/07/2007 

17/09/2007 

17/11/2007 

152

Frequency-Magnitude Relation 

for Cluster 1 

3.0 

Magnitude-Frequency Relation for Cluster 2 

2.5 

y = -1.62x + 0.71 

2.5 

LOG Cumulative Frequency 

2.0 

1.5 

1.0 

Log Cumulative Frequency 

2 

1.5 

1 

y = -1.27x + 0.53 

y = -2.17x + 0.07 

0.5 

0.5 

0.0 

-1.5 -1.0 -0.5 0.0 0.5 

0 

-1.5 -1 -0.5 0 0.5 

A 


B 


Magnitude-Frequency Relation for Cluster 3 

2.0 

LOG Cumulative Frequency 

1.5 

1.0 

0.5 

y = -1.30x + 0.10 

0.0 

-1.5 -1.0 -0.5 0.0 0.5 

C 

Moment Mangitude 

Figure B20: Magnitude-Frequency relations for (A) Cluster 1; (B) Cluster 2; and (C) Cluster 3. 

153

Appendix C 

Fault Plane Solutions 

Table C1 Fault Plane Solution Data for 7400 and 7530 Levels, January 1, 2006 – December 31, 2006 

154 

P-axis B-axis T-axis 

Fault Plane 

1 

Fault Plane 

2 

Event 

# 

Date Time Level Northing Easting Depth Trend Plunge Trend Plunge Trend Plunge Strike Dip Strike Dip fit% 

1 18/01/2006 5:10:49 7400 6153 4353 7371 226.0 33.0 324.0 12.0 72.0 54.0 147.0 79.0 276.0 17.0 84 

2 01/01/2006 6:30:27 7400 6231 4698 7325 92.0 4.0 190.0 64.0 0.0 26.0 43.0 75.0 139.0 69.0 80 

3 05/01/2006 11:05:48 7400 6238 4841 7372 244.0 68.0 358.0 10.0 92.0 20.0 354.0 66.0 199.0 26.0 78 

4 18/01/2006 20:11:40 7400 6182 4482 7341 306.0 32.0 50.0 21.0 168.0 50.0 347.0 24.0 238.0 80.0 81 

5 17/01/2006 3:38:14 7400 6222 4301 7417 250.0 8.0 150.0 49.0 347.0 40.0 125.0 69.0 20.0 56.0 77 

7 27/01/2006 4:12:13 7400 6548 4136 7386 354.0 19.0 259.0 17.0 129.0 64.0 251.0 66.0 110.0 30.0 88 

8 01/02/2006 2:26:41 7400 6187 4697 7348 247.0 15.0 135.0 55.0 346.0 31.0 119.0 79.0 22.0 57.0 77 

9 13/02/2006 3:18:51 7400 6276 4459 7445 298.0 16.0 90.0 72.0 205.0 8.0 341.0 73.0 72.0 84.0 77 

10 14/02/2006 6:12:52 7400 6096 4374 7306 227.0 13.0 327.0 38.0 121.0 49.0 165.0 68.0 279.0 46.0 75 

11 02/02/2006 13:30 7400 6150 4409 7352 219.0 75.0 125.0 1.0 34.0 15.0 123.0 30.0 305.0 60.0 84 

12 15/02/2006 17:33:06 7400 6134 4800 7348 294.0 9.0 44.0 66.0 201.0 22.0 204.0 81.0 340.0 68.0 81 

13 13/02/2006 3:56:38 7400 6327 4171 7294 244.0 65.0 127.0 12.0 33.0 21.0 312.0 67.0 102.0 26.0 83 

14 07/02/2006 17:59:48 7400 6005 4579 7351 53.0 10.0 146.0 19.0 298.0 68.0 339.0 57.0 121.0 39.0 82 

15 29/03/2006 13:23:26 7400 6160 4503 7347 307.0 40.0 156.0 46.0 50.0 15.0 353.0 74.0 97.0 50.0 81 

16 08/03/2006 18:51:35 7400 6137 4446 7300 221.0 25.0 327.0 31.0 100.0 49.0 155.0 76.0 266.0 34.0 83 

17 06/03/2006 13:30:48 7400 231.0 13.0 23.0 75.0 139.0 7.0 275.0 76.0 6.0 85.0 81 

18 19/03/2006 16:46:50 7400 6771 4867 7341 139.0 52.0 27.0 16.0 286.0 33.0 210.0 80.0 329.0 19.0 80 

19 01/04/2006 1:54:25 7400 6168 4421 7376 98.0 85.0 323.0 4.0 233.0 4.0 319.0 41.0 146.0 49.0 83 

20 21/04/2006 2:49:56 7400 6285 4472 7437 257.0 56.0 120.0 26.0 19.0 20.0 310.0 70.0 73.0 34.0 74 

21 21/04/2006 2:35:13 7400 6239 4498 7420 267.0 84.0 122.0 5.0 31.0 4.0 306.0 49.0 116.0 42.0 86 

22 30/05/2006 7:02:55 7400 6172 4318 7353 237.0 15.0 332.0 17.0 108.0 67.0 161.0 62.0 304.0 34.0 75


155 

Fault Plane 

1 

Fault Plane 

2 

Event 

# 


23 22/05/2006 2:21:29 7400 6185 4787 7433 86.0 40.0 338.0 21.0 228.0 42.0 337.0 89.0 244.0 21.0 80 

24 23/05/2006 8:30:33 7400 6275 4878 7376 52.0 2.0 321.0 36.0 145.0 54.0 293.0 57.0 173.0 53.0 76 

25 30/05/2006 7:02:55 7400 6172 4318 7353 239.0 18.0 335.0 16.0 103.0 65.0 162.0 65.0 305.0 30.0 75 

26 03/05/2006 8:25:31 7400 6170 4609 7315 291.0 20.0 121.0 70.0 22.0 3.0 335.0 79.0 68.0 74.0 74 

27 25/06/2006 10:19:17 7400 6066 4692 7379 241.0 21.0 137.0 34.0 356.0 48.0 125.0 74.0 14.0 39.0 88 

28 23/06/2006 5:34:19 7400 6342 4752 7442 225.0 79.0 29.0 10.0 120.0 3.0 221.0 43.0 20.0 49.0 75 

29 20/06/2006 4:47:23 7400 6372 4445 7455 92.0 2.0 186.0 64.0 1.0 26.0 44.0 74.0 140.0 71.0 68 

30 22/06/2006 14:44:03 7400 6205 4482 7307 140.0 12.0 246.0 52.0 41.0 35.0 86.0 75.0 187.0 56.0 83 

31 19/06/2006 9:38:09 7400 6246 4491 7424 5.0 82.0 123.0 4.0 312.0 7.0 120.0 52.0 307.0 38.0 75 

32 19/06/2006 12:32:56 7400 6085 4377 7346 87.0 6.0 356.0 7.0 217.0 81.0 350.0 51.0 185.0 40.0 75 

33 19/06/2006 2:19:03 7400 6115 4366 7330 306.0 1.0 214.0 68.0 36.0 22.0 173.0 75.0 79.0 74.0 77 

34 19/06/2006 14:38:09 7400 6149 4331 7332 229.0 50.0 135.0 3.0 43.0 40.0 316.0 85.0 104.0 6.0 80 

35 27/06/2006 7:41:46 7400 6291 4319 7451 165.0 3.0 258.0 46.0 73.0 44.0 110.0 63.0 219.0 59.0 83 

36 08/07/2006 11:18:25 7400 6390 4953 7399 215.0 58.0 9.0 29.0 106.0 11.0 227.0 42.0 353.0 62.0 77 

37 01/07/2006 13:07:24 7400 6321 4700 7459 36.0 69.0 274.0 12.0 180.0 17.0 100.0 63.0 253.0 30.0 89 

38 13/07/2006 23:50:42 7400 6331 4544 7451 166.0 31.0 50.0 36.0 284.0 39.0 47.0 85.0 310.0 37.0 83 

39 19/07/2006 20:56:36 7400 6315 4145 7325 116.0 10.0 207.0 9.0 337.0 76.0 33.0 56.0 195.0 36.0 85 

40 10/07/2006 22:01:32 7400 6411 4455 7447 85.0 29.0 206.0 43.0 333.0 33.0 28.0 88.0 121.0 43.0 72 

41 11/07/2006 3:14:05 7400 6198 4395 7419 265.0 7.0 167.0 50.0 0.0 39.0 139.0 69.0 35.0 58.0 77 

42 04/07/2006 11:18:42 7400 6185 4288 7292 248.0 23.0 30.0 62.0 15.0 35.0 21.0 85.0 288.0 62.0 81 

43 05/07/2006 9:11:35 7400 6085 4364 7300 53.0 4.0 150.0 59.0 321.0 31.0 3.0 72.0 102.0 65.0 76 

44 11/07/2006 6:15:13 7400 6127 4488 7310 281.0 10.0 157.0 73.0 13.0 14.0 147.0 87.0 57.0 74.0 73 

45 11/07/2006 8:01:54 7400 6156 4652 7316 258.0 1.0 166.0 64.0 348.0 26.0 126.0 73.0 30.0 71.0 71 

46 10/07/2006 22:19:51 7400 6248 4615 7441 240.0 26.0 49.0 64.0 148.0 4.0 281.0 69.0 17.0 75.0 75 

47 10/07/2006 21:17:18 7400 6186 4554 7378 55.0 78.0 255.0 11.0 164.0 4.0 85.0 50.0 242.0 42.0 78 

48 03/07/2006 23:57:07 7400 6126 4705 7379 205.0 22.0 302.0 18.0 68.0 61.0 129.0 69.0 265.0 28.0 81 

49 27/07/2006 8:54:53 7400 6251 4835 7406 241.0 55.0 149.0 1.0 58.0 35.0 330.0 80.0 142.0 10.0 81


156 

Fault Plane 

1 

Fault Plane 

2 

Event 

# 


50 10/07/2006 20:21:38 7400 6184 4580 7375 277.0 35.0 127.0 51.0 18.0 15.0 323.0 77.0 63.0 54.0 82 

51 10/07/2006 19:52:55 7400 6165 4553 7371 282.0 35.0 100.0 55.0 192.0 1.0 321.0 65.0 63.0 67.0 79 

52 11/07/2006 6:34:29 7400 6194 4638 7339 281.0 36.0 133.0 49.0 23.0 16.0 328.0 77.0 68.0 52.0 67 

53 15/07/2006 16:12:09 7400 6189 4674 7313 274.0 21.0 149.0 57.0 15.0 25.0 145.0 87.0 53.0 57.0 78 

54 11/07/2006 2:45:28 7400 6169 4613 7309 279.0 16.0 86.0 74.0 189.0 4.0 323.0 76.0 55.0 82.0 78 

55 06/08/2006 10:44:08 7400 6204 4737 7301 268.0 77.0 47.0 10.0 138.0 9.0 39.0 54.0 240.0 37.0 86 

56 04/08/2006 3:59:07 7400 6337 4815 7412 76.0 69.0 228.0 19.0 321.0 9.0 215.0 57.0 72.0 39.0 77 

57 04/08/2006 3:58:56 7400 6332 4837 7421 81.0 70.0 214.0 14.0 308.0 14.0 56.0 33.0 206.0 60.0 74 

58 06/08/2006 0:29:27 7400 6400 4914 7352 283.0 39.0 91.0 51.0 188.0 6.0 62.0 68.0 318.0 59.0 77 

59 02/09/2006 17:44:27 7400 6187 4648 7302 268.0 10.0 150.0 69.0 1.0 18.0 135.0 84.0 43.0 70.0 84 

60 05/09/2006 16:54:52 7400 6183 4621 7319 287.0 21.0 27.0 26.0 163.0 56.0 217.0 71.0 339.0 33.0 80 

61 29/09/2006 6:31:23 7400 6207 4561 7443 39.0 61.0 146.0 9.0 241.0 27.0 143.0 73.0 354.0 19.0 80 

62 26/09/2006 14:32:38 7400 6133 4497 7322 250.0 4.0 152.0 62.0 342.0 28.0 119.0 74.0 23.0 68.0 67 

63 01/09/2006 5:22:40 7400 6118 4425 7341 178.0 7.0 275.0 48.0 82.0 41.0 123.0 68.0 228.0 57.0 76 

64 01/09/2006 9:01:03 7400 6038 4343 7307 21.0 63.0 284.0 3.0 192.0 26.0 105.0 71.0 274.0 19.0 85 

65 04/09/2006 16:54:58 7400 6069 4337 7297 318.0 1.0 227.0 32.0 50.0 57.0 200.0 55.0 76.0 52.0 76 

66 11/09/2006 5:57:26 7400 6105 4359 7313 256.0 6.0 152.0 67.0 348.0 22.0 124.0 79.0 30.0 70.0 63 

67 01/09/2006 7:37:40 7400 6192 4296 7439 96.0 25.0 282.0 65.0 187.0 2.0 138.0 74.0 234.0 71.0 75 

68 17/10/2006 20:53:10 7400 6195 4617 7313 113.0 6.0 233.0 77.0 22.0 11.0 67.0 87.0 158.0 78.0 80 

69 02/10/2006 18:32:23 7400 6109 4324 7296 288.0 65.0 42.0 11.0 137.0 23.0 38.0 68.0 248.0 25.0 89 

70 28/11/2006 4:48:59 7400 6256 4562 7415 280.0 30.0 141.0 53.0 22.0 21.0 64.0 54.0 329.0 84.0 76 

71 29/11/2006 6:25:34 7400 6185 4553 7365 278.0 34.0 128.0 52.0 18.0 15.0 324.0 78.0 63.0 55.0 72 

72 19/11/2006 21:02:21 7400 6145 4347 7364 241.0 32.0 131.0 28.0 9.0 44.0 127.0 83.0 25.0 29.0 76 

73 19/11/2006 21:21:09 7400 6156 4384 7387 309.0 36.0 160.0 50.0 50.0 15.0 356.0 77.0 96.0 53.0 76 

74 29/11/2006 22:28:35 7400 6203 4309 7333 245.0 49.0 135.0 17.0 33.0 37.0 317.0 84.0 67.0 18.0 73 

75 29/11/2006 19:28:56 7400 6214 4677 7364 222.0 14.0 328.0 47.0 121.0 39.0 166.0 74.0 269.0 52.0 80 

76 29/11/2006 16:31:59 7400 6199 4656 7323 134.0 12.0 26.0 56.0 232.0 31.0 6.0 77.0 268.0 59.0 72

P-axis B-axis T-axis Fault Plane 1 Fault Plane 2 

Event 

# 


77 29/11/2006 6:05:52 7400 6225 4648 7361 101.0 22.0 351.0 40.0 213.0 42.0 341.0 78.0 238.0 42.0 76 

78 29/11/2006 1:51:20 7400 6193 4640 7345 306.0 27.0 59.0 37.0 189.0 41.0 244.0 82.0 345.0 38.0 73 

79 28/11/2006 17:53:00 7400 6251 4561 7418 77.0 61.0 261.0 29.0 170.0 2.0 106.0 53.0 234.0 50.0 68 

80 28/11/2006 15:18:50 7400 6172 4601 7295 302.0 49.0 172.0 29.0 66.0 26.0 359.0 77.0 111.0 33.0 74 

81 28/11/2006 14:45:47 7400 6264 4662 7451 338.0 19.0 236.0 32.0 94.0 52.0 223.0 71.0 108.0 38.0 78 

82 28/11/2006 11:06:18 7400 6207 4602 7310 285.0 4.0 162.0 82.0 15.0 7.0 150.0 88.0 60.0 82.0 73 

83 28/11/2006 7:52:47 7400 6193 4594 7324 295.0 34.0 169.0 41.0 48.0 31.0 351.0 88.0 83.0 41.0 79 

84 23/12/2006 4:30:58 7400 6157 4365 7317 259.0 33.0 129.0 44.0 9.0 27.0 313.0 86.0 46.0 45.0 61 

85 18/12/2006 18:21:56 7400 6083 4327 7295 286.0 26.0 191.0 10.0 81.0 62.0 187.0 72.0 39.0 21.0 77 

86 12/12/2006 14:41:35 7400 6076 4380 7322 177.0 42.0 53.0 32.0 301.0 32.0 237.0 84.0 336.0 32.0 70 

87 02/12/2006 7:15:39 7400 6102 4410 7420 297.0 68.0 112.0 22.0 203.0 2.0 93.0 51.0 314.0 47.0 74 

88 01/12/2006 22:39:49 7400 6129 4387 7352 55.0 2.0 152.0 74.0 324.0 16.0 8.0 80.0 100.0 77.0 86 

89 20/12/2006 3:45:59 7400 6392 4418 7399 100.0 12.0 296.0 77.0 190.0 3.0 144.0 84.0 236.0 79.0 76 

90 02/12/2006 4:25:22 7400 6187 4512 7347 154.0 41.0 0.0 33.0 256.0 13.0 304.0 51.0 199.0 73.0 67 

91 19/12/2006 3:58:22 7400 6155 4608 7301 263.0 61.0 173.0 0.0 83.0 29.0 353.0 74.0 172.0 16.0 82 

92 19/12/2006 1:20:12 7400 6169 4538 7317 267.0 33.0 153.0 33.0 30.0 40.0 150.0 86.0 54.0 33.0 78 

93 18/12/2006 18:35:32 7400 6046 4544 7429 212.0 3.0 306.0 56.0 120.0 33.0 161.0 69.0 262.0 65.0 81 

94 11/12/2006 12:38:37 7400 6179 4619 7322 287.0 20.0 64.0 64.0 190.0 16.0 59.0 88.0 328.0 64.0 74 

95 09/12/2006 2:50:36 7400 6134 4574 7389 107.0 8.0 352.0 71.0 199.0 17.0 334.0 84.0 242.0 72.0 89 

96 27/12/2006 23:50:14 7400 6163 4790 7366 250.0 25.0 46.0 63.0 156.0 10.0 25.0 79.0 290.0 65.0 72 

97 24/12/2006 1:47:58 7400 6159 4722 7375 286.0 15.0 27.0 36.0 177.0 50.0 223.0 69.0 337.0 44.0 70 

98 30/01/2006 3:36:39 7400 5907 4522 7461 66.0 30.0 175.0 29.0 300.0 46.0 360.0 81.0 106.0 30.0 73 

99 21/01/2006 11:51:09 7400 6281 4361 7467 80.0 51.0 227.0 34.0 329.0 17.0 212.0 70.0 98.0 41.0 72 

100 20/01/2006 9:41:03 7740 6277 4369 7462 187.0 37.0 88.0 12.0 343.0 50.0 86.0 83.0 327.0 13.0 76 

101 20/01/2006 4:01:19 7530 6344 4486 7525 319.0 58.0 54.0 3.0 147.0 32.0 54.0 77.0 249.0 13.0 70 

102 18/01/2006 7:33:27 7530 6334 4477 7508 95.0 14.0 251.0 75.0 4.0 6.0 139.0 76.0 230.0 85.0 79 

103 17/01/2006 23:08:20 7530 6306 4615 7519 357.0 71.0 96.0 3.0 187.0 19.0 94.0 64.0 282.0 26.0 82 

157


Event 

# 


104 17/01/2006 19:32:24 7530 6274 4821 7461 245.0 32.0 94.0 54.0 344.0 14.0 291.0 78.0 29.0 56.0 75 

105 17/01/2006 11:53:10 7530 6363 4394 7481 92.0 39.0 268.0 51.0 0.0 2.0 233.0 65.0 129.0 62.0 78 

106 17/01/2006 5:00:25 7530 6329 4686 7592 99.0 36.0 331.0 40.0 213.0 29.0 155.0 86.0 249.0 40.0 79 

107 16/01/2006 22:49:22 7530 6360 4526 7520 101.0 55.0 199.0 5.0 292.0 34.0 198.0 79.0 44.0 12.0 77 

108 16/01/2006 22:38:10 7530 6514 4488 7534 28.0 70.0 295.0 1.0 204.0 20.0 115.0 65.0 292.0 25.0 84 

109 16/01/2006 21:31:24 7530 6267 4404 7486 222.0 77.0 95.0 8.0 4.0 10.0 281.0 56.0 85.0 36.0 71 

110 16/01/2006 21:26:25 7400 6383 4399 7465 278.0 42.0 38.0 30.0 151.0 34.0 36.0 86.0 298.0 30.0 75 

111 13/01/2006 19:19:15 7400 6256 4578 7495 128.0 11.0 35.0 15.0 252.0 71.0 25.0 58.0 236.0 37.0 80 

112 05/01/2006 21:56:42 7400 6196 4584 7496 295.0 7.0 193.0 60.0 29.0 29.0 166.0 75.0 68.0 64.0 76 

113 21/02/2006 8:59:38 7400 6260 4339 7408 333.0 34.0 221.0 29.0 101.0 42.0 219.0 86.0 121.0 29.0 80 

114 20/02/2006 5:17:21 7400 6068 4372 7323 47.0 16.0 253.0 73.0 139.0 7.0 93.0 84.0 184.0 74.0 74 

115 20/02/2006 2:00:36 7400 6145 4354 7310 263.0 26.0 3.0 20.0 126.0 56.0 189.0 74.0 316.0 26.0 74 

116 19/02/2006 10:34:47 7400 6144 4349 7352 150.0 38.0 9.0 45.0 257.0 20.0 200.0 79.0 300.0 47.0 75 

117 19/02/2006 6:37:37 7400 6138 4348 7358 124.0 23.0 261.0 60.0 26.0 18.0 256.0 87.0 164.0 60.0 67 

118 19/02/2006 3:00:18 7400 6139 4332 7345 291.0 37.0 72.0 46.0 185.0 20.0 61.0 80.0 322.0 48.0 84 

119 19/02/2006 1:12:08 7400 6137 4379 7390 73.0 11.0 323.0 60.0 169.0 27.0 304.0 79.0 208.0 63.0 71 

120 17/02/2006 17:07:49 7400 6169 4326 7433 281.0 23.0 177.0 30.0 43.0 51.0 168.0 74.0 53.0 35.0 74 

121 17/02/2006 0:41:20 7400 6097 4384 7293 48.0 63.0 189.0 22.0 285.0 16.0 178.0 64.0 44.0 35.0 79 

122 16/02/2006 13:04:46 7400 6235 4346 7402 186.0 34.0 311.0 41.0 72.0 31.0 309.0 88.0 217.0 41.0 75 

123 16/02/2006 1:12:18 7400 6134 4359 7371 66.0 32.0 270.0 55.0 163.0 11.0 111.0 76.0 209.0 59.0 68 

124 15/02/2006 11:41:18 7400 6178 4301 7301 244.0 44.0 124.0 27.0 14.0 34.0 307.0 84.0 48.0 28.0 80 

125 14/02/2006 6:12:52 7400 6096 4374 7306 227.0 13.0 327.0 38.0 121.0 49.0 165.0 68.0 279.0 46.0 75 

126 14/02/2006 3:32:57 7400 6171 4366 7344 321.0 57.0 116.0 30.0 213.0 11.0 335.0 43.0 99.0 62.0 74 

127 13/02/2006 3:56:38 7400 6327 4171 7294 244.0 65.0 127.0 12.0 33.0 21.0 312.0 67.0 102.0 26.0 83 

128 13/02/2006 3:18:51 7400 6276 4459 7445 298.0 21.0 84.0 65.0 202.0 13.0 339.0 66.0 71.0 84.0 73 

129 13/02/2006 1:55:58 7400 6167 4354 7445 202.0 8.0 296.0 25.0 95.0 63.0 134.0 58.0 266.0 43.0 75 

130 12/02/2006 15:31:58 7400 6242 4313 7388 149.0 37.0 276.0 38.0 33.0 30.0 273.0 86.0 177.0 38.0 75 

158


Event 


# 

131 12/02/2006 4:24:22 7400 6135 4336 7385 299.0 20.0 43.0 34.0 184.0 49.0 235.0 73.0 347.0 39.0 72 

132 12/02/2006 3:54:59 7400 6193 4310 7348 173.0 2.0 81.0 38.0 265.0 52.0 52.0 58.0 295.0 54.0 73 

133 12/02/2006 1:29:21 7400 6271 4368 7328 262.0 49.0 130.0 30.0 24.0 25.0 318.0 77.0 69.0 34.0 67 

134 11/02/2006 10:53:51 7400 6268 4444 7410 250.0 60.0 159.0 0.0 69.0 30.0 340.0 75.0 159.0 15.0 77 

135 09/02/2006 23:32:50 7400 6075 4285 7291 312.0 47.0 100.0 38.0 203.0 17.0 85.0 72.0 334.0 44.0 73 

136 09/02/2006 18:04:04 7400 6163 4316 7363 270.0 21.0 176.0 9.0 65.0 67.0 172.0 67.0 16.0 25.0 68 

137 09/02/2006 3:16:41 7400 6161 4330 7440 248.0 26.0 342.0 7.0 86.0 63.0 164.0 72.0 321.0 20.0 81 

138 05/02/2006 15:07:30 7400 6228 4308 7404 291.0 10.0 44.0 67.0 197.0 21.0 335.0 68.0 242.0 82.0 72 

139 03/02/2006 23:50:12 7400 6177 4320 7351 156.0 24.0 273.0 45.0 47.0 35.0 100.0 83.0 196.0 45.0 79 

140 03/02/2006 18:33:38 7400 6180 4325 7413 162.0 51.0 271.0 15.0 12.0 35.0 269.0 82.0 150.0 17.0 67 

141 02/02/2006 7:22:05 7400 6190 4343 7320 315.0 28.0 183.0 52.0 59.0 24.0 6.0 87.0 98.0 52.0 74 

142 02/02/2006 6:58:23 7400 6175 4391 7390 191.0 20.0 288.0 18.0 57.0 62.0 116.0 68.0 252.0 30.0 78 

143 02/02/2006 6:56:09 7400 6192 4449 7419 337.0 9.0 239.0 39.0 77.0 49.0 217.0 65.0 103.0 50.0 65 

144 01/02/2006 12:46:13 7400 6140 4376 7371 85.0 7.0 319.0 77.0 176.0 10.0 311.0 88.0 221.0 78.0 68 

145 20/03/2006 9:12:41 7400 6229 4263 7328 69.0 23.0 244.0 67.0 338.0 2.0 206.0 75.0 111.0 73.0 82 

146 18/03/2006 20:43:26 7400 6189 4579 7366 269.0 13.0 160.0 54.0 7.0 32.0 142.0 77.0 43.0 57.0 62 

147 16/03/2006 13:30:48 7400 6232 4379 7422 231.0 15.0 25.0 73.0 139.0 7.0 274.0 74.0 6.0 84.0 81 

148 16/03/2006 13:30:46 7400 6262 4380 7420 230.0 28.0 35.0 61.0 136.0 6.0 6.0 75.0 269.0 66.0 82 

149 13/03/2006 3:47:31 7400 6249 4686 7298 235.0 29.0 118.0 39.0 350.0 37.0 114.0 85.0 18.0 40.0 83 

150 11/03/2006 14:03:05 7400 6233 4372 7365 225.0 73.0 98.0 11.0 5.0 13.0 81.0 33.0 284.0 59.0 72 

151 10/03/2006 0:38:25 7400 6362 4821 7458 69.0 70.0 184.0 9.0 277.0 18.0 180.0 63.0 21.0 28.0 82 

152 08/03/2006 18:51:35 7400 6137 4446 7300 215.0 29.0 311.0 10.0 58.0 59.0 134.0 75.0 279.0 18.0 78 

153 06/03/2006 3:07:20 7400 6217 4589 7458 257.0 25.0 143.0 40.0 9.0 39.0 136.0 82.0 37.0 41.0 75 

154 05/03/2006 18:42:15 7400 6190 4431 7325 271.0 7.0 170.0 56.0 6.0 32.0 143.0 73.0 44.0 62.0 79 

155 30/03/2006 19:51:46 7400 6130 4357 7361 109.0 5.0 226.0 79.0 19.0 10.0 64.0 87.0 154.0 80.0 74 

156 29/03/2006 13:23:26 7400 6160 4503 7347 284.0 55.0 159.0 22.0 58.0 26.0 346.0 74.0 108.0 28.0 77 

157 27/04/2006 0:49:12 7400 6296 4893 7381 109.0 48.0 292.0 42.0 200.0 2.0 144.0 59.0 256.0 57.0 79 

159


Event 


# 

158 26/04/2006 11:03:58 7400 6300 4839 7358 61.0 51.0 258.0 37.0 161.0 8.0 100.0 63.0 216.0 49.0 71 

159 24/04/2006 15:06:09 7400 6317 4871 7455 300.0 9.0 203.0 39.0 41.0 50.0 180.0 65.0 67.0 49.0 71 

160 22/04/2006 11:50:29 7400 6453 4883 7450 150.0 50.0 28.0 24.0 284.0 30.0 213.0 79.0 326.0 27.0 88 

161 21/04/2006 6:39:42 7400 6254 4465 7431 70.0 3.0 172.0 75.0 339.0 15.0 24.0 82.0 116.0 77.0 75 

162 21/04/2006 2:35:13 7400 6239 4498 7420 267.0 84.0 122.0 5.0 31.0 4.0 306.0 49.0 116.0 42.0 86 

163 15/04/2006 23:35:34 7400 6161 4340 7418 221.0 6.0 328.0 70.0 129.0 19.0 173.0 81.0 266.0 72.0 72 

164 13/04/2006 21:12:21 7400 6331 4344 7376 336.0 3.0 234.0 64.0 69.0 26.0 205.0 77.0 109.0 68.0 65 

165 12/04/2006 3:25:13 7400 6231 4659 7327 250.0 75.0 113.0 11.0 22.0 10.0 99.0 37.0 301.0 56.0 74 

166 07/04/2006 13:59:30 7400 6278 4466 7456 208.0 67.0 57.0 20.0 323.0 10.0 250.0 58.0 30.0 39.0 67 

167 04/04/2006 8:58:05 7400 6181 4386 7310 243.0 29.0 140.0 21.0 20.0 53.0 135.0 77.0 17.0 25.0 79 

168 03/04/2006 17:49:39 7400 6168 4316 7373 183.0 11.0 279.0 29.0 74.0 59.0 116.0 62.0 242.0 42.0 84 

169 03/04/2006 2:43:25 7400 6328 4789 7437 99.0 74.0 298.0 15.0 206.0 5.0 280.0 42.0 130.0 52.0 79 

170 02/04/2006 7:49:10 7400 6118 4331 7338 227.0 54.0 107.0 20.0 5.0 28.0 292.0 76.0 54.0 25.0 73 

171 30/05/2006 7:02:55 7400 6172 4318 7353 239.0 18.0 335.0 16.0 103.0 65.0 162.0 65.0 305.0 30.0 75 

172 27/05/2006 17:22:40 7400 6162 4347 7393 312.0 27.0 201.0 36.0 70.0 43.0 194.0 81.0 92.0 37.0 77 

173 15/05/2006 13:45:16 7400 6108 4374 7306 265.0 32.0 97.0 57.0 359.0 5.0 47.0 64.0 308.0 72.0 65 

174 06/05/2006 13:51:29 7400 6228 4340 7426 204.0 27.0 94.0 34.0 324.0 44.0 88.0 81.0 344.0 35.0 71 

175 30/05/2006 7:02:55 7400 6172 4318 7353 237.0 15.0 332.0 17.0 108.0 67.0 161.0 62.0 304.0 34.0 75 

176 27/05/2006 17:22:40 7400 6162 4347 7393 313.0 28.0 201.0 35.0 71.0 42.0 195.0 82.0 94.0 37.0 77 

177 23/05/2006 6:39:08 7400 6304 4887 7379 263.0 32.0 124.0 51.0 7.0 21.0 313.0 83.0 49.0 51.0 76 

178 09/05/2006 5:38:27 7400 6294 4759 7417 282.0 6.0 39.0 77.0 191.0 11.0 327.0 78.0 236.0 86.0 74 

179 09/05/2006 4:02:01 7400 6264 4710 7438 38.0 75.0 243.0 14.0 152.0 6.0 227.0 41.0 74.0 53.0 80 

180 09/05/2006 3:48:22 7400 6286 4693 7459 103.0 42.0 245.0 41.0 354.0 20.0 233.0 77.0 129.0 44.0 81 

181 05/05/2006 2:44:00 7400 6310 4880 7438 221.0 4.0 116.0 76.0 312.0 14.0 87.0 83.0 355.0 78.0 79 

182 03/05/2006 8:25:31 7400 6170 4609 7315 291.0 20.0 121.0 70.0 22.0 3.0 335.0 79.0 68.0 74.0 74 

183 30/06/2006 23:49:53 7400 6242 4764 7297 264.0 29.0 138.0 46.0 12.0 30.0 138.0 90.0 48.0 46.0 63 

184 27/06/2006 7:41:46 7400 6291 4319 7451 165.0 3.0 258.0 46.0 73.0 44.0 110.0 63.0 219.0 59.0 83 

160


Event 

# 


185 26/06/2006 4:16:07 7400 6257 4795 7378 220.0 73.0 74.0 14.0 342.0 9.0 55.0 38.0 264.0 56.0 74 

186 25/06/2006 10:19:17 7400 6066 4692 7379 197.0 45.0 96.0 11.0 355.0 43.0 276.0 89.0 10.0 11.0 82 

187 24/06/2006 18:56:57 7400 6159 4359 7367 357.0 28.0 106.0 32.0 235.0 45.0 292.0 80.0 38.0 34.0 77 

188 24/06/2006 0:53:35 7400 6349 4758 7438 43.0 64.0 159.0 12.0 254.0 23.0 154.0 69.0 7.0 25.0 84 

189 23/06/2006 17:24:50 7400 6188 4745 7362 213.0 70.0 303.0 0.0 34.0 20.0 303.0 65.0 124.0 25.0 82 

190 23/06/2006 5:34:19 7400 6342 4752 7442 47.0 86.0 199.0 4.0 290 2.0 23.0 43.0 196.0 47.0 67 

191 22/06/2006 14:44:03 7400 6205 4482 7307 140.0 12.0 246.0 52.0 41.0 35.0 86.0 75.0 187.0 56.0 83 

192 21/06/2006 15:54:34 7400 6186 4539 7389 318.0 23.0 193.0 54.0 60.0 26.0 190.0 88.0 98.0 54.0 80 

193 20/06/2006 4:47:23 7400 6367 4456 7496 92.0 2.0 182.0 64.0 1.0 26.0 44.0 74.0 140.0 71.0 68 

194 06/06/2006 4:02:43 7400 6130 4374 7437 50.0 21.0 176.0 57.0 310.0 24.0 360.0 88.0 91.0 58.0 69 

195 09/06/2006 16:31:39 7400 6202 4660 7352 87.0 44.0 264.0 46.0 355.0 1.0 122.0 60.0 230.0 62.0 89 

196 15/06/2006 19:07:06 7400 6150 4355 7368 17.0 6.0 282.0 38.0 115.0 51.0 257.0 61.0 141.0 51.0 67 

197 13/06/2006 3:27:21 7400 6087 4953 7375 18.0 25.0 208.0 64.0 109.0 4.0 61.0 75.0 156.0 69.0 69 

161

Appendix D 

Modelling Results 

D.1 UDEC Results 

Results for UDEC models are presented in this section. 

C = Cohesion, in MPa 

Ф = Friction angle, in degrees. 

162

D.1.1: Case 1 Models 

Figure D1: Case 1, elastic models showing maximum stress. (A) Locked condition. Pinks and reds indicate high stress; (B) C=5 MPa, Φ=35°; (C) C=0 MPa, 

Φ=35°; (D) C=0 MPa, Φ=20°. 

163

Figure D2: Case 1, elastic models showing differential stress. (A) Locked condition. Greens and yellow indicate high differential stress; (B) C=5, Φ=35°; (C) 

C=0, Φ=35°; (D) C=0, Φ=20°. 

164

Figure D3: Case 1, elastic models shear displacement along discontinuities. Green indicates right-lateral slip. (A) Locked condition; (B) C=5, Φ=35°; (C) C=0, 

Φ=35°; (D) C=0, Φ=20°. 

165

A B 

C D 

Figure D4: Case 1, plastic models showing major principal stress. Pinks and reds indicate high stress. (A) Locked condition; (B) C=5, Φ=35°; (C) C=0, Φ=35°; 

(D) C=0, Φ=20°. 

166

A B 

C D 

Figure D5: Case 1, plastic models showing differential stress. Greens and yellow indicate high differential stress. (A) Locked condition; (B) C=5, Φ=35°; (C) 

C=0, Φ=35°; (D) C=0, Φ=20°. 

167

A B 

C D 

Figure D6: Case 1, plastic model showing yielding. Purple indicates tensile failure; green and pink indicate past and current yielding. (A) Locked condition; (B) 

C=5, Φ=35°; (C) C=0, Φ=35°; (D) C=0, Φ=20°. 

168

A B 

C D 

Figure D7: Case 1, plastic models showing shear displacement along discontinuities. Green indicates right-lateral slip. (A) Locked condition; (B) C=5, Φ=35°; 

(C) C=0, Φ=35°; (D) C=0, Φ=20°. 

169

Figure D8: Stress distribution of elastic model, C=0, Φ=35°. 

Figure D9: Stress distribution of plastic model, C=0, Φ=35°. 

170


A B 

C D 

Figure D10: Case 2, elastic models for C=0, Φ =35º. (A) Major principal stress. Pinks and reds indicate high stress; (B) Differential stress. Yellow and greens 

indicate high differential stress; (C) assigned fault materials according to Table 4.3; (D) shear displacement along discontinuities. 

171

A B 

C D 

Figure D11: Case 2, plastic models for C=0, Φ =35º. (A) Major principal stress. Pinks and reds indicate high stress; (B) Differential stress. Yellow and greens 

indicate high differential stress; (C) Plastic yielding. Purple indicates tensile failures, green and pink indicate past and current yielding; (D) shear displacement 

along discontinuities. 

172


A B 

C 

Figure D12: Case 3 (k=2), elastic models for C=0, Φ =35º. (A) Major principal stress. Pinks and reds indicate high stress; (B) Differential stress. 

Yellow and greens indicate high differential stress; (C) shear displacement along discontinuities. 

173

A B 

C D 

Figure D13: Case 3 (k=2), plastic models for C=0, Φ =35º. (A) Major principal stress. Pinks and reds indicate high stress; (B) Differential stress. 

Yellow and greens indicate high differential stress; (C) Plastic yielding. Purple indicates tensile failures, green and pink indicate past and current 

yielding; (D) shear displacement along discontinuities. 

174

D1.4 Tectonic Loading Models 

Figure D14: Tectonic model, elastic models for C=0, Φ =35º. (A) Major principal stress. Pinks and reds indicate high stress; (B) Differential stress. 

Yellow and greens indicate high differential stress; (C) shear displacement along discontinuities. 

175

Figure D15: Tectonic model, plastic model for C=0, Φ =35º. (A) Major principal stress. Pinks and reds indicate high stress; (B) Differential stress. 

Yellow and greens indicate high differential stress; (C) Plastic yielding. Purple indicates tensile failures, green and pink indicate past and current 

yielding; (D) shear displacement along discontinuities. 

176

D.2 Discussion of Phase 2 Models 

Elastic and plastic models were created using the finite element method in Phase 2 (Rocscience, 

2005) to model the stress distribution resulting from geological structure and mining geometry on 

the 7200, 7400 and 7530 Levels. The modelling approach and results are discussed in this 

appendix. A comparison of results from Phase 2 and UDEC for the 7400 Level is also presented. 

D.2.1 Model Constituents 

Like UDEC models presented in Chapter 4, model geometry constructed in Phase 2 consists of: 

a) the model medium, whose geomechanical properties are modelled after footwall rocks in 

the Creighton Deep. Property values are taken or derived from values provided by 

Coulson (1996) for footwall rocks. Rock mass failure is governed by Mohr-Coulomb 

criteria (cohesion and friction). Values used in Phase 2 models are the same values used 

in UDEC models discussed in Chapter 4. 

b) pervasive joints that represent shear zones. Failure along these features is also governed 

by Mohr-Coulomb criteria. Like models created in UDEC, discontinuities in Phase 2 

models assume lateral continuity of shear zones, far beyond the excavation. 

c) the main excavation that was modelled after level plans provided by Vale Inco. This 

comprises stopes and sills in the 400 Orebody. 

Model constituents are shown in Figure D16. 

177

Figure D16 Phase 2 model depicting model and boundary conditions. The model consists of a rockmass, 

joints (orange) and an excavation, outlined in black. This figure shows the first stage in a two-stage model 

where material within the excavation removed in the second stage. 

D.2.2 Boundary Conditions 

The model is subject to an external stress field where the maximum principal stress is directed 

EW and the minimum principal stress is oriented NS. An intermediate, out-of-plane stress is 

applied in the vertical direction. Phase 2 uses a positive sign convention to denote compressive 

stress. Movement on the model boundaries is restricted by pinning the corners of the model so 

that NS or EW movement of the model is not possible. This is appropriate as it simulates the 

confined conditions of the mine within the Canadian Shield. 

178

Staged models were created in which the medium and discontinuities are allowed to come to 

equilibrium before introducing the excavation. In this manner the stress conditions simulate 

stress conditions within the mine and influence of the excavation on the distribution of stress can 

be better understood. This approach did not yield appreciable differences from the applying 

external stresses to a model complete with an excavation. 

Unlike models created in UDEC, tectonically loaded models were not created due to limitations 

on the program version. 

Phase 2 results are shown for Case 1, described in Chapter 4, in which all faults are assigned equal 

properties. Faults within the model are progressively weakened to induce slip by varying the 

cohesion and angle of internal friction. Material properties were also tested to examine the effect 

of rock mass strength on fault slip. 

D.3 Phase 2 Model Results 

Results for the 7200, 7400 and 7530 Level indicate that stress is bounded by faults rather than 

accumulated along weaker geological structure. This indicates that seismicity is a result of the 

stress concentrations that occurs between faults, rather than slip on the mine-scale structures. 

The stress distribution closely matches the distribution of seismicity in the January 2006- 

December 2007 time period. Areas of high maximum and differential stress are areas of dense 

event localization, while areas of low modelled stress are areas of sparse activity. In plastic 

models, yielding occurs directly to the north and south of the excavation and displacement is 

modelled along discontinuities within this yielded zone. Low stress is modelled in this yield zone 

and correspondingly, there is little-to no seismicity. 

179

The 7200 Level (Fig. D17) is an excellent example of how stress is modelled to be bounded and 

channelled between faults. To the north of the excavation, high stresses are concentrated between 

the Northwest and Fresh Air Raise Shear Zones, and bounded to the south by the Footwall Shear 

Zone. High stress is modelled between the Return Air Raise and Plum Shear Zones to the south 

of the excavation and is bounded to the north by the Footwall Shear Zone. This area corresponds 

to dense seismic activity. 

The 7400 Level (Fig. D18) model shows that high stress forms a ring around the excavation and 

is bounded by faults, lowering stress to the southwest of the excavation. NE-striking faults act to 

shield this area from high stress. Shear zones in this model act as a boundary to stress rather than 

a conduit or concentrator for stress. 

The 7530 Level model (Fig. D19) has similar excavation geometry as the 7400 Level and has a 

similar stress distribution. Stress is diminished in the southwest, as highlighted best in the elastic 

case (Fig. D19A, B) and is elevated in a ring around the excavation, as highlighted in the plastic 

case (Fig. D19C, D). High stress occurs between the Plum and Return Air Raise Shear Zones. 

Seismicity on this level occurs between the Plum and 402 Shear Zones and thus may not be 

accurately represented by the 7530 Level model. 

Damage domains are identified in Figure D20. The yield zone, damage zone and intact rock 

correspond to those modelled in UDEC. 

180

Figure D17 (A) Elastic model showing sigma-1 for the 7200 Level. Areas in white exceed the maximum 

stress on the scale; (B) Elastic model showing deviatoric stress; (C) Plastic model showing sigma-1; (D) 

Plastic model showing deviatoric stress; (E) Plastic model showing failure in shear and in tension; (F) 

seismicity corresponding to the 7200 Level for comparison with modelled stress. 

181

Figure D18 (A) Elastic model showing sigma-1 for the 7400 Level. Areas in white exceed the maximum 

stress on the scale; (B) Elastic model showing deviatoric stress; (C) Plastic model showing sigma-1; (D) 

Plastic model showing deviatoric stress; (E) Plastic model showing failure in shear and in tension; (F) 

seismicity corresponding to the 7400 Level for comparison with modelled stress. 

182

Figure D19 (A) Elastic model showing sigma-1 for the 7530 Level; (B) Elastic model showing deviatoric 

stress; (C) Plastic model showing sigma-1; (D) Plastic model showing deviatoric stress. Slip on faults is 

indicated in red; (E) Plastic model showing failure in shear and in tension; (F) seismicity corresponding to 

the 7530 Level for comparison with modelled stress. 

183

Figure D20 Rock mass states of degradation, as modelled for the 7400 Level in Phase 2 . 

D.4 Comparison of Phase 2 and UDEC Modelling Results 

The stress distribution in Phase 2 

results closely correspond to that modelled with UDEC. 

Differences in results using the two programs and numerical methods are reviewed. 

D.4.1 Similarities 

• The distribution of stress around the excavation on the 7400 Level is comparable to that 

in UDEC: Stress flows in a ring around the main excavation. This stress is intensified to 

the SE of the excavation and diminished in the SW. This result is comparable to the 

distribution of seismicity around the main excavation. Results are similar even with 

different initial loading conditions. 

184

• Similar damage zones surrounding the excavation are modelled in both programs with 

tensile deformation in proximity to the excavation and damage in shear beyond this. 

D.4.2 Differences 

• The modelled elevated differential stress in Phase2 is often restricted to the area between 

two shear zones (the Return Air Raise Shear Zone and Plum Shear Zone on the 7400 

Level, for example) or bounded by shear zones. This suggests that stress is bounded by 

shear zones. High stresses occur in stiffer rock rather than accumulated in weak zones. 

• In plastic models, yielding is restricted to a zone surrounding the excavation, similar to 

UDEC model results, but no yielding is modeled along shear zones. 

• Slip is induced on the Fresh Air Raise, Plum, 402 and Northwest Shear Zones to the 

south of the excavation. This slip occurs within the yield zone. This differs from slip 

modelled in UDEC, in which slip is only induced along the Plum and Fresh Air Raise 

Shear Zones. 

Model results produced using the distinct element method (UDEC) and finite element method 

(Phase 2 ) are very similar. The interactive visual display in Phase 2 and the minimal computing 

time required to produce a stress model make the finite element method a time-efficient way to 

model stress in two-dimensions in the Creighton Deep. The capabilities of UDEC are more 

robust. More detail is available for individual models and routines can be easily to expand the 

depth of the analysis. 

185

Appendix E 

UDEC Code 

E.1 Case 1: Variable fault strength parameters (Elastic model) 

;---------------------------------------------------------- 

;---- ---- 

;---- 7400L UDEC Elastic Model ---- 

;---- ---- 

;---------------------------------------------------------- 

round 0.5 

set edge 5.173 

; 

;========================================================== 

;===== define block =============================== 

;========================================================== 

block material 1 0,0 0,1564.64 1564.64,1564.64 1564.64,0 

; 

;========================================================== 

;===== define excavation ========================== 

;========================================================== 

crack (670.56,793.496) (670.56,815.848) 

crack (670.56,815.848) (726.44,832.612) 

crack (726.44,832.612) (815.848,832.612) 

crack (815.848,832.612) (815.848,843.788) 

crack (815.848,843.788) (877.316,843.788) 

crack (877.316,843.788) (922.02,804.672) 

crack (922.02,804.672) (922.02,787.404) 

crack (922.02,787.404) (888.492,773.007) 

crack (888.492,773.007) (888.492,736.410) 

crack (888.492,736.410) (866.14,726.44) 

crack (866.14,726.44) (838.2,737.616) 

crack (838.2,737.616) (815.848,771.144) 

crack (815.848,771.144) (815.848,782.32) 

crack (815.848,782.32) (748.792,782.32) 

crack (748.792,782.32) (743.204,793.496) 

crack (743.204,793.496) (670.56,793.496) 

; 

;========================================================== 

;===== define sub block ============================ 

;========================================================== 

crack (447.04,447.04) (447.04,1117.6) 

crack (447.04,1117.6) (1117.6,1117.6) 

crack (1117.6,1117.6) (1117.6,447.04) 

crack (1117.6,447.04) (447.04,447.04) 

; 

;========================================================== 

;===== define faults ============================== 

;========================================================== 

crack (0,251.92736) (1564.64,820.8772) 

crack (0,290.59632) (1564.64,859.54616) 

crack (0,355.2371429) (1564.64,1025.84504) 

crack (0,392.0061829) (1564.64,1062.61408) 

crack (0,437.4605714) (1564.64,1107.98864) 

crack (0,482.1629749) (1564.64,1158.05712) 

crack (0,1309.295) (1564.64,307.925) 

crack (905.676,730.681) (864.557,605.485) 

crack (845.579,718.676) (787.063,578.045) 

crack (807.625,780.415) (746.192,713.585) 

186

; 

;========================================================== 

;===== assign material properties ================= 

;========================================================== 

PROP mat=1 dens=0.002965 k=24613 g=13856 fric=35 coh=10 

PROP jmat=1 jkn=700000 jks=99400 jcoh=5 jfric=35 jtens=0 


change mat=1 range 0,1564.64 0,1564.64 

change jmat=1 range 0,1564.64 0,1564.64 

change jmat=2 range 446,1118, 446,448 

change jmat=2 range 446,1118 1117,1118 



; 

;========================================================== 

;===== Mohr-Coulomb Elastic Material =============== 

;========================================================== 

CHANGE cons 1 range 0,1564.64 0,1564.64 

; 

;========================================================== 

;===== null material to excavate ================== 

;========================================================== 

CHANGE cons 0 range 668,925 781,853 


; 

;========================================================== 

;===== Discretize ================================= 

;========================================================== 

gen edge 20.0 

; 

;========================================================== 

;===== set initial stress conditions ============== 

;========================================================== 

bound stress -102.70,0,0 range -1,1 0,1564.64 

bound stress -102.70,0,0 range 1563.64,1565.64 0,1564.64 

bound stress 0,0,-73.43 range 0,1564.64 -1,1 

bound stress 0,0,-73.43 range 0,1564.64 1563.64,1565.64 

insitu stress -102.70, 0, -73.43 

INITIAL sxx -102.70 

INITIAL syy -73.43 

INITIAL szz -83.43 

; 

;========================================================== 

;===== Set boundary velocity to zero ============== 

;========================================================== 

BOUNDARY yvel=0.0 range 0,1564.64 -1,1 

BOUNDARY yvel=0.0 range 0,1564.64 1563,1565 

BOUNDARY xvel=0.0 range -1,1 0,1564.64 

BOUNDARY xvel=0.0 range 1563,1565 0,1564.64 

; 

;========================================================== 

;===== time steps ================================= 

;========================================================== 

hist unbal 

hist xvel(50,50) 

hist yvel(50,50) 

hist xdisp(50,50) 

hist ydisp(50,50) 

SOLVE step 10000 

set plot po color 

187

E.2 Case 1: Variable fault strength parameters (Plastic model) 

;---------------------------------------------------------- 

;---- ---- 

;---- 7400L UDEC PLASTIC MODEL ---- 

;---- ---- 

;---------------------------------------------------------- 

; 

round 0.5 


; 

;========================================================== 

;===== define block =============================== 

;========================================================== 


; 

;========================================================== 


;========================================================== 

crack (670.56,793.496) (670.56,815.848) 

crack (670.56,815.848) (726.44,832.612) 

crack (726.44,832.612) (815.848,832.612) 

crack (815.848,832.612) (815.848,843.788) 

crack (815.848,843.788) (877.316,843.788) 

crack (877.316,843.788) (922.02,804.672) 

crack (922.02,804.672) (922.02,787.404) 

crack (922.02,787.404) (888.492,773.007) 

crack (888.492,773.007) (888.492,736.410) 

crack (888.492,736.410) (866.14,726.44) 

crack (866.14,726.44) (838.2,737.616) 

crack (838.2,737.616) (815.848,771.144) 

crack (815.848,771.144) (815.848,782.32) 

crack (815.848,782.32) (748.792,782.32) 

crack (748.792,782.32) (743.204,793.496) 

crack (743.204,793.496) (670.56,793.496) 

; 

;========================================================== 


;========================================================== 

crack (447.04,447.04) (447.04,1117.6) 

crack (447.04,1117.6) (1117.6,1117.6) 

crack (1117.6,1117.6) (1117.6,447.04) 

crack (1117.6,447.04) (447.04,447.04) 

; 

;========================================================== 

;===== define faults ============================== 

;========================================================== 

crack (0,251.92736) (1564.64,820.8772) 

crack (0,290.59632) (1564.64,859.54616) 

crack (0,355.2371429) (1564.64,1025.84504) 

crack (0,392.0061829) (1564.64,1062.61408) 

crack (0,437.4605714) (1564.64,1107.98864) 

crack (0,482.1629749) (1564.64,1158.05712) 

crack (0,1309.295) (1564.64,307.925) 

; 

;========================================================== 


;========================================================== 





188


change jmat=2 range 446,1118, 446,448 




; 

;========================================================== 

;===== elasto-plastic Mohr-Coulomb ================ 

;========================================================== 


; 

;========================================================== 


;========================================================== 

CHANGE cons 0 range 670.560,922.020 726.440,843.788 

; 

;========================================================== 

;===== Discretize ================================= 

;========================================================== 

gen edge 20.0 

; 

;========================================================== 


;========================================================== 





insitu stress -102.70, 0, -73.43 




; 

;========================================================== 


;========================================================== 





; 

;========================================================== 

;===== time steps ================================= 

;========================================================== 

hist unbal 







plot hold sig1 fill bl 

189

E.3 Case 2: Variable Fault Strength by Shear Zone Family (Elastic Model) 

;---------------------------------------------------------- 

;---- ---- 

;---- 7400L UDEC MODEL ---- 

;---- VARIABLE FAULT STRENGTH ---- 

;---- Elastic Model ---- 

;---- ---- 

;---------------------------------------------------------- 

; 

round 0.5 


;========================================================== 

;===== define block =============================== 

;========================================================== 


;========================================================== 


;========================================================== 

crack (670.56,793.496) (670.56,815.848) 

crack (670.56,815.848) (726.44,832.612) 

crack (726.44,832.612) (815.848,832.612) 

crack (815.848,832.612) (815.848,843.788) 

crack (815.848,843.788) (877.316,843.788) 

crack (877.316,843.788) (922.02,804.672) 

crack (922.02,804.672) (922.02,787.404) 

crack (922.02,787.404) (888.492,773.007) 

crack (888.492,773.007) (888.492,736.410) 

crack (888.492,736.410) (866.14,726.44) 

crack (866.14,726.44) (838.2,737.616) 

crack (838.2,737.616) (815.848,771.144) 

crack (815.848,771.144) (815.848,782.32) 

crack (815.848,782.32) (748.792,782.32) 

crack (748.792,782.32) (743.204,793.496) 

crack (743.204,793.496) (670.56,793.496) 

;========================================================== 


;========================================================== 

crack (447.04,447.04) (447.04,1117.6) 

crack (447.04,1117.6) (1117.6,1117.6) 

crack (1117.6,1117.6) (1117.6,447.04) 

crack (1117.6,447.04) (447.04,447.04) 

;========================================================== 

;===== define faults ============================== 

;========================================================== 

;===FAR-type=== 

crack (0,251.92736) (1564.64,820.8772) 

;===FAR=== 

crack (0,290.59632) (1564.64,859.54616) 

;===plum=== 

crack (0,355.2371429) (1564.64,1025.84504) 

;===402=== 

crack (0,392.0061829) (1564.64,1062.61408) 

;===RAR=== 

crack (0,437.4605714) (1564.64,1107.98864) 

;===NW=== 

crack (0,482.1629749) (1564.64,1158.05712) 

;===FW=== 

crack (0,1309.295) (1564.64,307.925) 

;===Splays=== 

crack (905.676,730.681) (864.557,605.485) 

190

crack (845.579,718.676) (787.063,578.045) 

crack (807.625,780.415) (746.192,713.585) 

;===1290/400E=== 

crack (0,806.814) (670.243,806.814) 

crack (670.243,806.814) (922.184,789.484) 

crack (922.184,789.484) (1564.64,789.484) 

; 

;========================================================== 


;========================================================== 







; 


; 

change jmat=3 range 0,1564.64 246,1171 angle 15,30 

; 

change jmat=2 range -1,1565 303,1324 angle 140,160 

; 

change jmat=4 range 446,1118, 446,448 angle -1,1 

change jmat=4 range 446,1118 1117,1118 angle -1,1 

change jmat=4 range 446,448 446,1118 angle 89,91 


; 

;========================================================== 


;========================================================== 


; 

;========================================================== 


;========================================================== 



PAUSE 

;========================================================== 

;===== Discretize ================================= 

;========================================================== 

gen edge 20.0 

; 

;========================================================== 


;========================================================== 





insitu stress -102.70, 0, -73.43 




;========================================================== 


;========================================================== 





191

;========================================================== 

;===== time steps ================================= 

;========================================================== 

hist unbal 








E.4 Case 2: Variable Fault Strength by Shear Zone Family (Plastic Model) 

;---------------------------------------------------------- 

;---- ---- 

;---- 7400L UDEC MODEL ---- 

;---- VARIABLE FAULT STRENGTH ---- 

;---- Plastic Model ---- 

;---- ---- 

;---------------------------------------------------------- 

; 

round 0.5 


;========================================================== 

;===== define block =============================== 

;========================================================== 


;========================================================== 


;========================================================== 

crack (670.56,793.496) (670.56,815.848) 

crack (670.56,815.848) (726.44,832.612) 

crack (726.44,832.612) (815.848,832.612) 

crack (815.848,832.612) (815.848,843.788) 

crack (815.848,843.788) (877.316,843.788) 

crack (877.316,843.788) (922.02,804.672) 

crack (922.02,804.672) (922.02,787.404) 

crack (922.02,787.404) (888.492,773.007) 

crack (888.492,773.007) (888.492,736.410) 

crack (888.492,736.410) (866.14,726.44) 

crack (866.14,726.44) (838.2,737.616) 

crack (838.2,737.616) (815.848,771.144) 

crack (815.848,771.144) (815.848,782.32) 

crack (815.848,782.32) (748.792,782.32) 

crack (748.792,782.32) (743.204,793.496) 

crack (743.204,793.496) (670.56,793.496) 

;========================================================== 


;========================================================== 

crack (447.04,447.04) (447.04,1117.6) 

crack (447.04,1117.6) (1117.6,1117.6) 

crack (1117.6,1117.6) (1117.6,447.04) 

crack (1117.6,447.04) (447.04,447.04) 

;========================================================== 

;===== define faults ============================== 

;========================================================== 

;===FAR-type=== 

crack (0,251.92736) (1564.64,820.8772) 

;===FAR=== 

crack (0,290.59632) (1564.64,859.54616) 

192

;===plum=== 

crack (0,355.2371429) (1564.64,1025.84504) 

;===402=== 

crack (0,392.0061829) (1564.64,1062.61408) 

;===RAR=== 

crack (0,437.4605714) (1564.64,1107.98864) 

;===NW=== 

crack (0,482.1629749) (1564.64,1158.05712) 

;===FW=== 

crack (0,1309.295) (1564.64,307.925) 

;===Splays=== 

crack (905.676,730.681) (864.557,605.485) 

crack (845.579,718.676) (787.063,578.045) 

crack (807.625,780.415) (746.192,713.585) 

;===1290/400E=== 

crack (0,806.814) (670.243,806.814) 

crack (670.243,806.814) (922.184,789.484) 

crack (922.184,789.484) (1564.64,789.484) 

; 

;========================================================== 


;========================================================== 


; 






; 


;(EW structures and splays) 

; 

change jmat=3 range 0,1564.64 246,1171 angle 15,30 

;(NE-trending structures) 

; 

change jmat=2 range -1,1565 303,1324 angle 140,160 

;(FW fault) 

; 





;(locked box) 

; 

;========================================================== 


;========================================================== 


; 

;========================================================== 


;========================================================== 



PAUSE 

;========================================================== 

;===== Discretize ================================= 

;========================================================== 

gen edge 20.0 

; 

;========================================================== 

193


;========================================================== 





insitu stress -102.70, 0, -73.43 




;========================================================== 


;========================================================== 





;========================================================== 

;===== time steps ================================= 

;========================================================== 

hist unbal 





; 




;END 

E.5 Case 3: Increased Principal Stress Ratio (Elastic Model) 

;---------------------------------------------------------- 

;---- ---- 

;---- 7400L UDEC MODEL ---- 

;---- Elastic Stress Ratio K=2 ---- 

;---- ---- 

;---------------------------------------------------------- 

; 

round 0.5 


;========================================================== 

;===== define block =============================== 

;========================================================== 


;========================================================== 


;========================================================== 

crack (670.56,793.496) (670.56,815.848) 

crack (670.56,815.848) (726.44,832.612) 

crack (726.44,832.612) (815.848,832.612) 

crack (815.848,832.612) (815.848,843.788) 

crack (815.848,843.788) (877.316,843.788) 

crack (877.316,843.788) (922.02,804.672) 

crack (922.02,804.672) (922.02,787.404) 

crack (922.02,787.404) (888.492,773.007) 

crack (888.492,773.007) (888.492,736.410) 

crack (888.492,736.410) (866.14,726.44) 

194

crack (866.14,726.44) (838.2,737.616) 

crack (838.2,737.616) (815.848,771.144) 

crack (815.848,771.144) (815.848,782.32) 

crack (815.848,782.32) (748.792,782.32) 

crack (748.792,782.32) (743.204,793.496) 

crack (743.204,793.496) (670.56,793.496) 

;========================================================== 


;========================================================== 

crack (447.04,447.04) (447.04,1117.6) 

crack (447.04,1117.6) (1117.6,1117.6) 

crack (1117.6,1117.6) (1117.6,447.04) 

crack (1117.6,447.04) (447.04,447.04) 

;========================================================== 

;===== define faults ============================== 

;========================================================== 

crack (0,251.92736) (1564.64,820.8772) 

crack (0,290.59632) (1564.64,859.54616) 

crack (0,355.2371429) (1564.64,1025.84504) 

crack (0,392.0061829) (1564.64,1062.61408) 

crack (0,437.4605714) (1564.64,1107.98864) 

crack (0,482.1629749) (1564.64,1158.05712) 

;===FW=== 

crack (0,1309.295) (1564.64,307.925) 

;===Splays=== 

crack (905.676,730.681) (864.557,605.485) 

crack (845.579,718.676) (787.063,578.045) 

crack (807.625,780.415) (746.192,713.585) 

;===1290/400E=== 

crack (0,806.814) (670.243,806.814) 

crack (670.243,806.814) (922.184,789.484) 

crack (922.184,789.484) (1564.64,789.484) 

; 

;========================================================== 


;========================================================== 






; 





; 

;========================================================== 


;========================================================== 


; 

;========================================================== 


;========================================================== 



PAUSE 

;========================================================== 

;===== Discretize ================================= 

;========================================================== 

gen edge 20.0 

195

; 

;========================================================== 


;========================================================== 



bound stress 0,0,-51 range 0,1564.64 -1,1 

bound stress 0,0,-51 range 0,1564.64 1563.64,1565.64 

insitu stress -102.70, 0, -51 


INITIAL syy -51 


;========================================================== 


;========================================================== 





;========================================================== 

;===== time steps ================================= 

;========================================================== 

hist unbal 








E.6 Case 3: Increased Principal Stress Ratio (Plastic Model) 

;---------------------------------------------------------- 

;---- ---- 

;---- 7400L UDEC MODEL ---- 

;---- Plastic Stress Ratio K=2 ---- 

;---- ---- 

;---------------------------------------------------------- 

; 

round 0.5 


;========================================================== 

;===== define block =============================== 

;========================================================== 


;========================================================== 


;========================================================== 

crack (670.56,793.496) (670.56,815.848) 

crack (670.56,815.848) (726.44,832.612) 

crack (726.44,832.612) (815.848,832.612) 

crack (815.848,832.612) (815.848,843.788) 

crack (815.848,843.788) (877.316,843.788) 

crack (877.316,843.788) (922.02,804.672) 

crack (922.02,804.672) (922.02,787.404) 

crack (922.02,787.404) (888.492,773.007) 

crack (888.492,773.007) (888.492,736.410) 

crack (888.492,736.410) (866.14,726.44) 

crack (866.14,726.44) (838.2,737.616) 

196

crack (838.2,737.616) (815.848,771.144) 

crack (815.848,771.144) (815.848,782.32) 

crack (815.848,782.32) (748.792,782.32) 

crack (748.792,782.32) (743.204,793.496) 

crack (743.204,793.496) (670.56,793.496) 

;========================================================== 


;========================================================== 

crack (447.04,447.04) (447.04,1117.6) 

crack (447.04,1117.6) (1117.6,1117.6) 

crack (1117.6,1117.6) (1117.6,447.04) 

crack (1117.6,447.04) (447.04,447.04) 

;========================================================== 

;===== define faults ============================== 

;========================================================== 

crack (0,251.92736) (1564.64,820.8772) 

crack (0,290.59632) (1564.64,859.54616) 

crack (0,355.2371429) (1564.64,1025.84504) 

crack (0,392.0061829) (1564.64,1062.61408) 

crack (0,437.4605714) (1564.64,1107.98864) 

crack (0,482.1629749) (1564.64,1158.05712) 

;===FW=== 

crack (0,1309.295) (1564.64,307.925) 

;===Splays=== 

crack (905.676,730.681) (864.557,605.485) 

crack (845.579,718.676) (787.063,578.045) 

crack (807.625,780.415) (746.192,713.585) 

;===1290/400E=== 

crack (0,806.814) (670.243,806.814) 

crack (670.243,806.814) (922.184,789.484) 

crack (922.184,789.484) (1564.64,789.484) 

; 

;========================================================== 


;========================================================== 






; 





; 

;========================================================== 


;========================================================== 


; 

;========================================================== 


;========================================================== 



PAUSE 

;========================================================== 

;===== Discretize ================================= 

;========================================================== 

gen edge 20.0 

; 

197

;========================================================== 


;========================================================== 



bound stress 0,0,-51 range 0,1564.64 -1,1 

bound stress 0,0,-51 range 0,1564.64 1563.64,1565.64 

insitu stress -102.70, 0, -51 




;========================================================== 


;========================================================== 





;========================================================== 

;===== time steps ================================= 

;========================================================== 

hist unbal 








E.7 Tectonic Loading Model (Elastic Model) 

;---------------------------------------------------------- 

;---- ---- 

;---- 7400L UDEC MODEL ---- 

;---- ELASTIC TECTONIC LOADING MODEL ---- 

;---- ---- 

;---------------------------------------------------------- 

; 

round 0.5 


;========================================================== 

;===== define block =============================== 

;========================================================== 


;========================================================== 


;========================================================== 

crack (670.56,793.496) (670.56,815.848) 

crack (670.56,815.848) (726.44,832.612) 

crack (726.44,832.612) (815.848,832.612) 

crack (815.848,832.612) (815.848,843.788) 

crack (815.848,843.788) (877.316,843.788) 

crack (877.316,843.788) (922.02,804.672) 

crack (922.02,804.672) (922.02,787.404) 

crack (922.02,787.404) (888.492,773.007) 

crack (888.492,773.007) (888.492,736.410) 

crack (888.492,736.410) (866.14,726.44) 

crack (866.14,726.44) (838.2,737.616) 

crack (838.2,737.616) (815.848,771.144) 

198

crack (815.848,771.144) (815.848,782.32) 

crack (815.848,782.32) (748.792,782.32) 

crack (748.792,782.32) (743.204,793.496) 

crack (743.204,793.496) (670.56,793.496) 

;========================================================== 


;========================================================== 

crack (447.04,447.04) (447.04,1117.6) 

crack (447.04,1117.6) (1117.6,1117.6) 

crack (1117.6,1117.6) (1117.6,447.04) 

crack (1117.6,447.04) (447.04,447.04) 

;========================================================== 

;===== define faults ============================== 

;========================================================== 

crack (0,251.92736) (1564.64,820.8772) 

crack (0,290.59632) (1564.64,859.54616) 

crack (0,355.2371429) (1564.64,1025.84504) 

crack (0,392.0061829) (1564.64,1062.61408) 

crack (0,437.4605714) (1564.64,1107.98864) 

crack (0,482.1629749) (1564.64,1158.05712) 

;===FW=== 

crack (0,1309.295) (1564.64,307.925) 

;===Splays=== 

crack (905.676,730.681) (864.557,605.485) 

crack (845.579,718.676) (787.063,578.045) 

crack (807.625,780.415) (746.192,713.585) 

;===1290/400E=== 

crack (0,806.814) (670.243,806.814) 

crack (670.243,806.814) (922.184,789.484) 

crack (922.184,789.484) (1564.64,789.484) 

; 

;========================================================== 


;========================================================== 






; 





; 

;========================================================== 


;========================================================== 


; 

;========================================================== 


;========================================================== 



PAUSE 

;========================================================== 

;===== Discretize ================================= 

;========================================================== 

gen edge 15.0 

; 

;========================================================== 

199


;========================================================== 

;***initial hydrostatic stress*** 

INITIAL sxx -85 


INITIAL szz -85 

;***rollers with compressed boundaries*** 





;insitu stress -102.70, 0, -73.43 

;========================================================== 

; 

;========================================================== 

;===== time steps ================================= 

;========================================================== 

hist unbal 








E.8 Tectonic Loading Model (Plastic Model) 

;---------------------------------------------------------- 

;---- ---- 

;---- 7400L UDEC MODEL ---- 

;---- PLASTIC TECTONIC LOADING MODEL ---- 

;---- ---- 

;---------------------------------------------------------- 

; 

round 0.5 


;========================================================== 

;===== define block =============================== 

;========================================================== 


;========================================================== 


;========================================================== 

crack (670.56,793.496) (670.56,815.848) 

crack (670.56,815.848) (726.44,832.612) 

crack (726.44,832.612) (815.848,832.612) 

crack (815.848,832.612) (815.848,843.788) 

crack (815.848,843.788) (877.316,843.788) 

crack (877.316,843.788) (922.02,804.672) 

crack (922.02,804.672) (922.02,787.404) 

crack (922.02,787.404) (888.492,773.007) 

crack (888.492,773.007) (888.492,736.410) 

crack (888.492,736.410) (866.14,726.44) 

crack (866.14,726.44) (838.2,737.616) 

crack (838.2,737.616) (815.848,771.144) 

crack (815.848,771.144) (815.848,782.32) 

crack (815.848,782.32) (748.792,782.32) 

crack (748.792,782.32) (743.204,793.496) 

crack (743.204,793.496) (670.56,793.496) 

;========================================================== 

200


;========================================================== 

crack (447.04,447.04) (447.04,1117.6) 

crack (447.04,1117.6) (1117.6,1117.6) 

crack (1117.6,1117.6) (1117.6,447.04) 

crack (1117.6,447.04) (447.04,447.04) 

;========================================================== 

;===== define faults ============================== 

;========================================================== 

crack (0,251.92736) (1564.64,820.8772) 

crack (0,290.59632) (1564.64,859.54616) 

crack (0,355.2371429) (1564.64,1025.84504) 

crack (0,392.0061829) (1564.64,1062.61408) 

crack (0,437.4605714) (1564.64,1107.98864) 

crack (0,482.1629749) (1564.64,1158.05712) 

;===FW=== 

crack (0,1309.295) (1564.64,307.925) 

;===Splays=== 

crack (905.676,730.681) (864.557,605.485) 

crack (845.579,718.676) (787.063,578.045) 

crack (807.625,780.415) (746.192,713.585) 

;===1290/400E=== 

crack (0,806.814) (670.243,806.814) 

crack (670.243,806.814) (922.184,789.484) 

crack (922.184,789.484) (1564.64,789.484) 

; 

;========================================================== 


;========================================================== 






; 





; 

;========================================================== 


;========================================================== 


; 

;========================================================== 


;========================================================== 



PAUSE 

;========================================================== 

;===== Discretize ================================= 

;========================================================== 

gen edge 15.0 

; 

;========================================================== 


;========================================================== 

;***initial hydrostatic stress*** 

INITIAL sxx -85 


201

INITIAL szz -85 

;***rollers with compressed boundaries*** 





;insitu stress -102.70, 0, -73.43 

;========================================================== 

; 

;========================================================== 

;===== time steps ================================= 

;========================================================== 

hist unbal 








202

E.9 S3:S1 Model for fracture reactivation 

;---------------------------------------------------------- 

;---- ---- 

;---- 7400L UDEC MODEL ---- 

;---- ---- 

;---------------------------------------------------------- 

; 

round 0.5 


;========================================================== 

;===== define block =============================== 

;========================================================== 


;========================================================== 


;========================================================== 

crack (670.56,793.496) (670.56,815.848) 

crack (670.56,815.848) (726.44,832.612) 

crack (726.44,832.612) (815.848,832.612) 

crack (815.848,832.612) (815.848,843.788) 

crack (815.848,843.788) (877.316,843.788) 

crack (877.316,843.788) (922.02,804.672) 

crack (922.02,804.672) (922.02,787.404) 

crack (922.02,787.404) (888.492,773.007) 

crack (888.492,773.007) (888.492,736.410) 

crack (888.492,736.410) (866.14,726.44) 

crack (866.14,726.44) (838.2,737.616) 

crack (838.2,737.616) (815.848,771.144) 

crack (815.848,771.144) (815.848,782.32) 

crack (815.848,782.32) (748.792,782.32) 

crack (748.792,782.32) (743.204,793.496) 

crack (743.204,793.496) (670.56,793.496) 

;========================================================== 


;========================================================== 

crack (447.04,447.04) (447.04,1117.6) 

crack (447.04,1117.6) (1117.6,1117.6) 

crack (1117.6,1117.6) (1117.6,447.04) 

crack (1117.6,447.04) (447.04,447.04) 

;========================================================== 

;===== define faults ============================== 

;========================================================== 

crack (0,251.92736) (1564.64,820.8772) 

crack (0,290.59632) (1564.64,859.54616) 

crack (0,355.2371429) (1564.64,1025.84504) 

crack (0,392.0061829) (1564.64,1062.61408) 

crack (0,437.4605714) (1564.64,1107.98864) 

crack (0,482.1629749) (1564.64,1158.05712) 

;===FW=== 

crack (0,1309.295) (1564.64,307.925) 

;===Splays=== 

crack (905.676,730.681) (864.557,605.485) 

crack (845.579,718.676) (787.063,578.045) 

crack (807.625,780.415) (746.192,713.585) 

;===1290/400E=== 

crack (0,806.814) (670.243,806.814) 

crack (670.243,806.814) (922.184,789.484) 

crack (922.184,789.484) (1564.64,789.484) 

; 

;========================================================== 


203

;========================================================== 






; 





; 

;========================================================== 


;========================================================== 


; 

;========================================================== 


;========================================================== 



;========================================================== 

;===== Discretize ================================= 

;========================================================== 

gen edge 20.0 

; 

;========================================================== 


;========================================================== 





insitu stress -102.70, 0, -73.43 




;========================================================== 


;========================================================== 





;========================================================== 

;===== time steps ================================= 

;========================================================== 

hist unbal 







; 

def ratios3s1 

bi=block_head 

loop while bi#0 

zi=b_zone(bi) 

loop while zi#0 

xval= abs(z_sxx(zi)) 

204

yval= abs(z_syy(zi)) 

xyval= abs(z_sxy(zi)) 

subt=abs(xval-yval) 

s1 = 0.5*(xval+yval) + sqrt(subt*subt+4*xyval*xyval) 

s3 = 0.5*(xval+yval) - sqrt(subt*subt+4*xyval*xyval) 

ratio = s3/s1 

z_extra(zi)=ratio 

zi=z_next(zi) 

endloop 

bi=b_next(bi) 

endloop 

end 

ratios3s1 

plot hold z_extra fill block 

E.9.1 FISH Routine: ratio s3s1.fis 

def ratios3s1 

bi=block_head 

loop while bi#0 

zi=b_zone(bi) 

loop while zi#0 

xval= z_sxx(zi) 

yval= z_syy(zi) 

xyval= z_sxy(zi) 

s1 = 0.5*(xval+yval) + sqrt((xval-yval)*(xval-yval)+4*xyval*xyval) 

s3 = 0.5*(xval+yval) - sqrt((xval-yval)*(xval-yval)+4*xyval*xyval) 

ratio = s3/s1 

z_extra(zi)=ratio 

zi=z_next(zi) 

endloop 

bi=b_next(bi) 

endloop 

end 

ratios3s1 

plot fill z_extra block 

205

Appendix F 

Fracture Reactivation 

F.1 Maximum-to-minimum Principal Stress Ratio 

Mapping fracture reactivation, as done in Chapter 4, is a function of the maximum-to minimum 

principal stress ratio. This is described in terms of the friction angle when there is no cohesion. 

Using the Mohr-Coulomb failure envelope as well as the Mohr circle, the Sine Law can be 

written as 

, (Equation F1) 

as shown in for triangle PBR in Figure F.1. 

Figure F1: Mohr-Coulomb failure envelope with Mohr circle depicting angles and quantities used in 

derivation 

Defining lengths BR and PB, 

(Equation F2) 

These can be substituted into Equation F1, 

206 

(Equation F3)

and rearranged to 


. (Equation F5) 

There are two intersections of the Mohr Circle with the Mohr-Coulomb failure envelope and thus 

two angles at which slip can occur: 

and 

(Equation F6) 


When cohesion is reduced to zero, these angles can be expressed as: 

(Equation F8) 


For the argument, 



By defining the maximum normal and shear stress, 

(Equation F12) 


the ratio of these quantities can be defined in terms of the maximum and minimum principal 

stress, 

207


Substituting this definition into equation 11, 


this ratio can be states as: 


This is the definition used to contour areas of slip in Chapter 4, based on the friction angle. 

F.2 Definitions for Deviatoric and Differential Stress 

Differential and deviatoric stress are plotted in UDEC and Phase 2 , respectively. There exists a 

need to define these parameters. Differential stress is defined as 

. 

It is a scalar quantity and is not to be confused with deviatoric stress, which defined by a tensor. 

Notation used to describe the deviatoric stress tensor is that used by Jaeger et al., (2007). 

The deviatoric stress tensor is obtained from subtracting the isotropic component of the stress 

tensor 


, 

where τ m is the mean of the principal stresses, from the full stress tensor, (Equation F18) 

208

Such that 


I is the identity matrix, 



The resulting deviatoric tensor takes the form 


Principal deviatoric stresses have the same orientation as principal stresses and are defined as: 




209

title of the thesis - Department of Geology - Queen's University

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