Advances in Geophysics (eBook)

Earth Heterogeneity and Scattering Effects on Seismic Waves

Michael Fehler, Haruo Sato (Herausgeber)

eBook Download: EPUB

2009 | 1. Auflage
496 Seiten
Elsevier Science (Verlag)
978-0-08-088033-4 (ISBN)

Infos

Seismic waves generated by earthquakes have been interpreted to provide us information about the Earth's structure across a variety of scales. For short periods less than 1 second, the envelope of seismograms changes significantly with increased travel distance and coda waves are excited by scattering due to randomly distributed heterogeneities in the Earth. Deterministic structures such as horizontally uniform velocity layer models in traditional seismology cannot explain these phenomena. This book focuses on the Earth heterogeneity and scattering effects on seismic waves. Topics covered are recent developments in wave theory and observation including: coda wave analysis for mapping medium heterogeneity and monitoring temporal variation of physical properties, radiation of short-period seismic waves from an earthquake fault, weak localization of seismic waves, attenuation of seismic waves in randomly porous media, synthesis of seismic wave envelopes in short periods, laboratory investigations of ultrasonic wave propagation in rock samples.


*Understanding new methods for the analysis of short-period seismic waves to characterize the random heterogeneity of the Earth on many scales.
*Observations of seismic wave scattering. Discussion of techniques for mapping medium heterogeneity and for monitoring temporal change in medium characteristics.
* Up-to-date techniques for the synthesis of wave envelopes in random media.

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Seismic waves generated by earthquakes have been interpreted to provide us information about the Earth's structure across a variety of scales. For short periods of less than 1 second, the envelope of seismograms changes significantly with increased travel distance and coda waves are excited by scattering due to randomly distributed heterogeneities in the Earth. Deterministic structures such as horizontally uniform velocity layer models in traditional seismology cannot explain these phenomena. This book focuses on the Earth heterogeneity and scattering effects on seismic waves. Topics covered are recent developments in wave theory and observation including: coda wave analysis for mapping medium heterogeneity and monitoring temporal variation of physical properties, radiation of short-period seismic waves from an earthquake fault, weak localization of seismic waves, attenuation of seismic waves in randomly porous media, synthesis of seismic wave envelopes in short periods, and laboratory investigations of ultrasonic wave propagation in rock samples. - Understanding new methods for the analysis of short-period seismic waves to characterize the random heterogeneity of the Earth on many scales- Observations of seismic wave scattering- Discussion of techniques for mapping medium heterogeneity and for monitoring temporal change in medium characteristics- Up-to-date techniques for the synthesis of wave envelopes in random media

Inhalt

Front Cover 1
Advances in Geophysics 4
Copyright Paage 5
Dedication Page 6
Contents 8
Contributors 16
Preface 18
Chapter 1: Coherent Back-Scattering and Weak Localization of Seismic Waves 22
1. Introduction 22
2. Weak Localization Effect: A Heuristic View 24
3. The Role of Source Mechanism and Wavefield Polarization 27
3.1. Effect of Source Mechanism 27
3.2. Review of Multiple Scattering Formalism 28
3.3. Theoretical Results for Acoustic and Elastic Waves 31
4. Geophysical Applications 34
4.1. Measurement of the Dispersion Relation of Surface Waves 34
4.2. Measurement of the Diffusion Constant in Strongly Scattering Media 37
5. Conclusion 38
Acknowledgments 38
References 38
Chapter 2: Theory of Transmission Fluctuations in Random Media with a Depth-Dependent Background Velocity Structure 42
1. Introduction 42
2. Acoustic Waves in Stratified Media and WKBJ Green Function 44
3. Rytov Solution to the Wave Equation in a Heterogeneous Medium 46
4. Complex Phase psi Due to a Plane Wave Incidence 47
5. Coherence Function Between Two Plane Waves 50
6. Coherence Functions Using Delta-Correlated Assumption 54
7. Coherence Functions in a Constant Background Medium 55
8. Numerical Examples 55
9. Validity of the Delta-Correlated Assumption 57
10. Discussions and Conclusions 58
Acknowledgments 59
Appendix:. Random Variables, Random Functions 59
References 60
Chapter 3: Synthesis of Vector-Wave Envelopes in Random Elastic Media on the Basis of the Markov Approximation 64
1. Introduction 65
1.1. Markov Approximation for the Wave Envelope Synthesis 65
1.2. Analyses of Seismogram Envelopes 66
1.3. Objectives 69
2. Vector-Wave Envelopes for the Plane Wavelet Incidence 72
2.1. Three-Dimensional Random Elastic Media 72
2.2. Two-Dimensional Random Elastic Media 85
3. Vector-Wave Envelopes for the Radiation from a Point Source 90
3.1. Three-Dimensional Random Elastic Media 90
3.2. Two-Dimensional Random Elastic Media 99
4. Discussions 104
4.1. RTT with the Born Approximation Scattering Coefficients 104
4.2. Realistic ACFs for Random Media 106
5. Summary 107
Acknowledgments 108
Appendix: Analytic Solutions of the Stochastic Master Equations for TFMCF 108
Plane Wave in Three Dimensions 108
Plane Wave in Two Dimensions 109
Spherical Wave in Three Dimensions 110
Cylindrical Wave in Two Dimensions 111
References 111
Chapter 4: Geometrical Optics of Acoustic Media with Anisometric Random Heterogeneities: Travel-Time Statistics of Reflected and Refracted Waves 116
1. Introduction 116
2. Basic Elements of the GO Method 118
2.1. Basic Equations of the GO 118
2.2. Model of Quasi-Homogeneous Fluctuations of Medium Parameters 120
2.3. Travel-Time Covariance Function in a Medium with Anisometric Fluctuations 121
2.4. Boundary of GO Applicability 122
3. Travel-Time Fluctuations in Reflection Geometry 123
3.1. Reflection Geometry 123
3.2. Travel-Time Covariance Function for Small Offsets 125
3.3. Double Passage Effect 127
4. Travel-Time Fluctuations in Refraction Geometry 128
4.1. Refracting Medium with a Constant Velocity Gradient 128
4.2. Travel-Time Variance along a Curvilinear Ray 129
4.3. Dependence of Travel-Time Variance on Offset 131
4.4. Inverse Problem Solution for Refraction Geometry 133
5. Results of Numerical Simulations 136
6. Discussion and Conclusion 139
Acknowledgements 141
References 141
Chapter 5: Attenuation of Seismic Waves Due to Wave-Induced Flow and Scattering in Randomly Heterogeneous Poroelastic Continua 144
1. Introduction 144
2. Meso- and Macroscopic Heterogeneity in the Earth and its Description as a Random Medium 147
3. Attenuation and Dispersion of Seismic Waves due to Wave-Induced Flow 150
3.1. Biot's Equations of Dynamic Poroelasticity and Associated Green's Functions 150
3.2. The Basic Poroelastic Scattering Equation 154
3.3. First-Order Statistical Smoothing Approximation 155
3.4. Effective Fast Wave Number Accounting for Conversion Scattering into Slow P Waves 156
3.5. Attenuation and Dispersion due to Wave-Induced Flow 159
3.6. Asymptotic Behavior at Low and High Frequencies 166
4. Attenuation of Seismic Waves in Random Porous Media due to Scattering 169
4.1. The Generalized ODA Formalism 169
4.2. Effective Wave Number in 3-D Random Media 170
4.3. Scattering Attenuation and Asymptotic Behavior 175
5. The Interplay Between Attenuation Due Interlayer Flow and Scattering 178
5.1. 1-D Poroelastic Random Media 178
5.2. Asymptotic Scaling of Attenuation 180
6. Concluding Remarks 183
Acknowledgments 184
References 185
Chapter 6: Observing and Modeling Elastic Scattering in the Deep Earth 188
1. Introduction 188
2. Data Stacking 189
2.1. Shallow- Versus Deep-Earthquake Teleseismic P Coda 191
2.2. Regional Variations in Teleseismic P Coda Amplitude 191
3. Monte Carlo Methods 195
3.1. Seismology Applications 196
3.2. Monte Carlo Implementation 197
3.3. The Monte Carlo Source 198
3.4. Particle Trajectories 199
3.5. Scattering Angles 202
3.6. Intrinsic Attenuation 206
4. Fit to Teleseismic P Coda 208
5. Conclusions 209
Acknowledgments 211
References 211
Chapter 7: A Scattering Waveguide in the Heterogeneous Subducting Plate 216
1. Introduction 217
2. Anomalous Intensity Patterns from Two Deep Events in the Subducted Philippine Sea Plate and in the Subducted Pacific Plate 219
2.1. Separation of Low-Frequency Precursors and High-Frequency Coda 222
2.2. Frequency Selective Propagation Properties in the Subducting Plate 222
3. 2D FDM Modeling of Scattering Wavefield 225
4. 2D FDM Modeling of Slab Guided Waves 229
4.1. Base Model: High-Q and High-V Subduction Zone 229
4.2. Heterogeneous Plate Model: Isotropic Heterogeneities in the Plate 231
4.3. Anisotropic Heterogeneities in the Plate 232
4.4. Effect of Plate Thickness 234
4.5. Effect of Heterogeneity Scale in the Plate 235
5. Discussion and Conclusion 236
Acknowledgments 237
References 237
Chapter 8: Laboratory Experiments of Seismic Wave Propagation in Random Heterogeneous Media 240
1. Introduction 240
2. Laboratory Experiments 242
2.1. Statistical Description of Heterogeneity 242
2.2. Wave Fields in Random Media 244
3. Scale-Invariant Expression 248
4. Waveform Analysis 251
4.1. Travel-Time Fluctuation 252
4.2. Cross Spectra Between Waves 252
4.3. Shear-Wave Particle Velocities 257
4.4. Waveform Envelope 259
5. Key Features of Wave Fluctuation in Random Media 261
5.1. Masking Signal Waves by Small-Scale Heterogeneities 261
5.2. Boundary Between EHM and SRM 262
5.3. Diffraction of Scattered Waves 263
6. Conclusions 264
6.1. Validity of Equivalent Homogeneous Medium Assumption 264
6.2. Random Media Effect on Seismic Data Processing 265
6.3. Role of Laboratory Experiments for Studying Seismic Wave Propagation 265
Acknowledgments 265
References 266
Chapter 9: Measurements of the Earth at the Scale of Logs, Crosswells, and VSPs 268
1. Introduction 268
2. Acoustic Logging 270
2.1. Dipole Logging 271
2.2. Modern Array Processing 271
2.3. Depth of Investigation 274
3. Crosswell Seismic Survey 276
3.1. Resolution of a Crosswell Seismic Survey 277
4. Vertical Seismic Profiling 280
5. Discussions and Summary 282
Acknowledgements 283
References 283
Chapter 10: Coda Energy Distribution and Attenuation 286
1. Introduction 286
2. Coda Energy Distribution and Measurement on QPminus,S1 using Local Seismograms 289
2.1. Uniformity of Coda Energy Distribution 289
2.2. Nonuniform Coda Energy Distribution in Tectonically Active Regions 294
3. Temporal Decay Rate of Coda Energy: QCminus1 299
3.1. Lapse-Time Dependence 299
3.2. Frequency Dependence 300
3.3. Geographic Variation 302
3.4. Temporal Variation 305
3.5. Models to Explain the Spatio-Temporal Correlation Between QC-1 and Seismicity 310
4. Closing Remarks 313
Acknowledgments 314
References 314
Chapter 11: Imaging Inhomogeneous Structures in the Earth by Coda Envelope Inversion and Seismic Array Observation 322
1. Introduction 322
2. Analysis of Seismic Network Data 323
2.1. Inversion of Coda Envelope 323
2.2. Kirchhoff Coda Migration 327
3. Analysis of Seismic Array Data 328
3.1. Detection of Seismic Signals by Array Observations 328
3.2. Single-Scattering Model for Seismic Array 330
3.3. Characteristics of Coda Waves Based on Array Observations 332
3.4. ScatterersolInhomogeneity Distribution Inferred from Seismic Array Data 333
4. Summary 336
Acknowledgments 337
References 337
Chapter 12: Source Effects From Broad Area Network Calibration of Regional Distance Coda Waves 340
1. Introduction 340
2. Data Analysis 342
3. Coda Calibration Methodology 347
3.1. Coda Start Time Calibration 352
3.2. Coda Shape Calibration and Amplitude Measurement 352
3.3. Intrastation Site Calibration 354
3.4. 2-D Path and Interstation Site Calibration 356
3.5. Source to Coda Transfer Function 361
4. Coda Spectral Results 363
5. Discussion 366
6. Conclusions 369
Acknowledgments 370
References 370
Chapter 13: Seismic Wave Scattering in Volcanoes 374
1. Introduction 374
1.1. Volcanic Earthquakes 374
1.2. A Brief Review of Coda-Qminus1 Observation on Volcanoes 375
2. Separated Estimates of Intrinsic and Scattering Attenuation 378
2.1. The Method of Wennerberg 379
2.2. The Energy-Flux Model 380
2.3. 2-D Transport Theory Applied to Volcanic Tremor 381
3. Diffusion Model Applied to Shot Data 382
3.1. Uniform Half Space 382
3.2. Two-Layer Media 384
4. Energy-Transport Theory Applied to Earthquake Data 386
4.1. Uniform Half Space 386
4.2. Possible Bias Introduced by Assuming a Uniform Diffusive Layer 387
4.3. Coda-Localization Effects 387
5. Concluding Remarks 388
Acknowledgments 390
References 390
Chapter 14: Monitoring Temporal Variations of Physical Properties in the Crust by Cross-Correlating the Waveforms of Seismic Doublets 394
1. Introduction 395
2. Selection of Doublets 395
3. Basic Processing 396
3.1. Time Delays Measured from Cross-Correlation or Cross-Spectrum 396
3.2. Cross-Spectral Moving Window or Cross-Correlation Moving Window Technique 398
4. Relocating Doublets from P and S Travel-Time Delays 399
4.1. Double-Difference Location 399
4.2. Two Synthetic Examples with IASP91 Travel Times 400
4.3. Possible Technical and Intrinsic Difficulties 401
5. An Example of Observed Delays: An Excellent Doublet in Japan 403
6. Slope of the Delay in the Coda and the Measurement of S-Velocity Temporal Variation 405
7. Possible Artifacts in DeltaVS/VS Measurement: Arguments from the Coda of Spatial Doublets 406
8. Search for Temporal Variation of S-Wave Splitting 410
9. Search for Temporal Variation of Coda Attenuation 411
10. "Virtual Doublets" Computed by Cross-Correlating Seismic Noise 412
11. PKP From Teleseismic Doublets and the Rotation of the Inner Core 414
12. Conclusion 416
Acknowledgements 416
References 416
Chapter 15: Seismogram Envelope Inversion for High-Frequency Seismic Energy Radiation from Moderate-to-Large Earthquakes 422
1. Introduction 423
2. Envelope Inversion Methods 424
2.1. General Framework 424
2.2. A Classification of Current Envelope Inversion Methods 425
2.3. The Method of Nakahara et al. (1998) 427
3. Data Analysis and the Results 432
3.1. An Example of Practical Data Analysis 432
4. Compilation of the Results 434
4.1. Frequency Dependence of High-Frequency Seismic Energy 435
4.2. Scaling of High-Frequency Seismic Energy 438
4.3. Spatial Relationship Between Asperities and High-Frequency Sources 441
5. Conclusions 444
Acknowledgments 445
References 445
Chapter 16: On the Random Nature of Earthquake Sources and Ground Motions: a Unified Theory 448
1. Introduction 448
2. Random Model of Earthquakes Slip Spatial Distribution and Consequences for the Ground Motions 450
2.1. From the Source hellip 450
2.2. hellip to the Ground Motion 454
3. The 2004 Parkfield Earthquake 456
3.1. Random Model of the Source 456
3.2. Random Model of the Ground Motion PGA 461
3.3. Random Model of the Ground Motion PGV 464
4. The 1999 Chi-Chi Earthquake 465
4.1. Random Model of the Source 465
4.2. Random Model of the Ground Motion PGA 466
5. Limitations of the Model 469
6. Conclusion: From Randomness to Invariance 475
Acknowledgments 476
Appendix. Generalization of the Random Model of the Radiated Field 476
A.1. Near-Field Displacement 476
A.2. Product of Random Variables 477
References 479
Glossary 484
Index 490

Produkt-Details

• Erscheint lt. Verlag: 26.2.2009
• Mitarbeit: Herausgeber (Serie): Renata Dmowska
• Sprache: englisch
• Themenwelt: Sachbuch/Ratgeber
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Geologie
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Geophysik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie
• Themenwelt: Technik
• ISBN-10: 0-08-088033-9 / 0080880339
• ISBN-13: 978-0-08-088033-4 / 9780080880334