Digital Seismology

PREFACE v

Chapter1. Source Determination and Discrimination between Earthquakes and Artificial Explosions 1
1-1 Auto-pick Up Technology for Earthquakes in and around the Korean Peninsula Using Waveform Format Conversion and Composition 3
1-1-1 Introduction 3
1-1-2 Data Acquisition and FESNET Array 5
1-1-3 Basic Theory and Source Determination 7
1-1-4 Comparision of the Results from FESNET with Those of Other Arrays 18
1-1-5 Discussion and Conclusion 18
Reference 20

1-2 Study on Some Characteristics of Earthquakes and Explosions Using the Polarization Method 21
1-2-1 Introduction 21
1-2-2 Method and Analysis 22
1-2-3 Discussion and Conclusions 35
Reference 35

1-3 Uncertainties of Seismic Source Determination Using a 3-Component Single Station 36
1-3-1 Introduction 36
1-3-2 Azimuth Estimation and Its Uncertainty 37
1-3-3 Uncertainties from Subjective Causes: Selection of Waveforms and the Time-Direction Stacking Approach 39
1-3-4 Uncertainly of Epicenter Distance 44
1-3-5 Discussion and Conclusions 45
Reference 46

1-4 Empirical Analysis of Digital Seismograms from a Cluster of Explosions at Regional Distances for Characterizing Multiple Explosions 47
1-4-1 Introduction 47
1-4-2 Empirical Analysis of Digital Seismograms from Explosions at Regional Distances 47
1-4-3 Similarities of Seismograms from Nearby Explosions at Regional Distances 50
1-4-4 Characterizing a Possible Multiple Explosion Using Empirical Synthetic Seismograms 51
1-4-5 Discussion and Conclusions 58
Reference 58

1-5 Discrimination of Small Earthquakes and Artificial Explosions in the Korean Peninsula Using Pg/Lg Ratio 60
1-5-1 Introduction 60
1-5-2 Data 61
1-5-3 Data Analysis and Interpretation 61
1-5-4 Discussion and Conclusions 69
Reference 69

Chapter 2. Focal Mechanism Solution Using Moment Tensor Inversion 71
2-1 Introduction 73
2-2 Earthquake Data Collection and Analysis 76
2-3 Basic Theory of Moment Tensor Inversion 81
2-4 Non-unique Problems on Focal Mechanism Solution 86
2-5 Discussion and Conclusions 93
Reference 95

Chapter 3. Double-Difference Method (hypoDD) for Source Relocation 97
3-1 Introduction 99
3-2 Basic Theory of Double-difference Algorithm 101
3-3 Data Acquisition and Earthquake Relocation 103
3-4 Interpretation and Discussion of Results: Relationship between Focal Mechanism and Hypocenters redetermined by HypoDD 113
3-5 Discussion and Conclusions 128
Reference 131
Appendix 3
A3-1 Travel Times of P- and S-wave Arrivals for Southern Korea 133
A3-2 Input Parameter File for ph2dt Program 189
A3-3 Output Logfile for ph2dt Program 190
A3-4 Corrected Input Data for a Pair of Events for Southern Korea 191
A3-5 Input Parameter File for hypoDD Program 198
A3-6 Output Log File 200

Chapter 4. Seismic Tomograpcchy 237
4-1 P- and S-wave Tomographic Imaging of the Crust and Uppermost Mantle beneath the Korean Peninsula 239
4-1-1 Introduction 239
4-1-2 Data and Method 240
4-1-3 Results 249
4-1-4 Error analysis and resolution tests 261
4-1-5 Discussion 265
4-1-6 Conclusions 267
Reference 269
Appendix 4-1
A4-1-1 Flowchart of Tomography Algorithm 273
A4-1-2 Stations in and arround the Korean Peninsuls 276
A4-1-3 Initial Source Parameters and Travel Times for the Korean Peninsula 283

4-2 Tectonic Features of Plate Juncture in Hokkaido, Japan Derived from Local Tomographic Inversion of P- and S-wave Travel Times 370
4-2-1 Introduction 370
4-2-2 Tectonic Setting 372
4-2-3 Data Acquisition and Analysis 374
4-2-4 Basic Theory of Inversion Algorithm 379
4-2-5 Interpretation of the Results 385
4-2-6 Error and Resolution Analysis 391
4-2-7 Discussion and Conclusion 395
Reference 398
Appendix 4-2
A4-2-1 The L1-norm 402
A4-2-2 Bouguer gravity map of Hokkaido, Japan 409
A4-2-3 Geology of Hokkaido 410

4-3 Changes in Ascent of Magma Body Batch Before and After Eruptions in Mt. Usu and Tokachi-dake, Hokkaido, Japan Using Volcanic Tomography 411
4-3-1 Introduction 412
4-3-2 Data Acquisition and Analysis 413
4-3-3 Geological and Geophysical Information 415
4-3-4 Basic Theory of Algorithm 416
4-3-5 Interpretation of Velocity Anomalies of Vp, Vs and Vp/Vs 423
4-3-6 Error and Resolution Analysis 429
4-3-7 Discussion and Conclusions 433
Reference 434
Appendix 4-3
A4-3-1 Construction of Matrix M × N(Amn) and Ax＝u for Volcanic Tomography 437
A4-3-2 CPU Times for Calculation for Each Region 439
A4-3-3 Input Parameters for Each Region 440
A4-3-4 Computer Output for Tokachi-dake 442
A4-3-5 Determination of Ray-density and Node for Tokachi-dake 447
A4-3-6 Computation of Various for Inverse Problems in Tokachi-dake 453
A4-3-7 Analysis of Error Reduction Rate for Tokachi-dake in Invbig.f 456

Chapter 5. Seismotechtonics of Mongolia Based on Earthquake Catalogue and Focal Mechanism 461
5-1 Introduction 464
5-2 Earthquake Catalogue of Mongolia 466
5-3 Seismicity and Seismic Hazard Evaluation of Mongolia 473
5-4 Focal Mechanism Solutions and Tectonics of Mongolia 475
5-5 Discussion and Conclusions 488
Reference 490
Appendix 5
A5-1 Earthquake Catalogue of Mongolia 492

INDEX 577