Foundations of Modern Global Seismology

Description

Modern Global Seismology, Second Edition, is a complete, self-contained primer on seismology, featuring extensive coverage of all related aspects―from observational data through prediction―and emphasizing the fundamental theories and physics governing seismic waves, both natural and anthropogenic. Based on thoroughly class-tested material, the text provides a unique perspective on Earth’s large-scale internal structure and dynamic processes, particularly earthquake sources, and the application of theory to the dynamic processes of the earth’s upper layer. This insightful new edition is designed for accessibility and comprehension for graduate students entering the field. Exploration seismologists will also find it an invaluable resource on topics such as elastic-wave propagation, seismic instrumentation, and seismogram analysis. 00 Front Matter Copyright_2021_Foundations-of-Modern-Global-Seismology Dedication_2021_Foundations-of-Modern-Global-Seismology Contents_2021_Foundations-of-Modern-Global-Seismology Contents Preface_2021_Foundations-of-Modern-Global-Seismology Preface Preface Part I - Observational foundations of global seismology Part II: Theoretical foundations of seismology 01 1 An overview of global seismology 1.1 The foundation of seismology: seismograms 1.2 The historical development of global seismology 1.3 The topics of global seismology 1.3.1 Seismic sources 1.3.2 Earthquake sources involving shear faulting 1.3.3 Seismic waves and seismograms 1.3.4 Quantification of earthquakes 1.3.5 Earthquake geographic distributions 1.3.6 Global faulting patterns and earthquake models 1.3.7 Earth's interior: radial Earth layering 1.3.8 Heterogeneous Earth models 1.3.9 Summary 1.4 Appendix: Great earthquakes, 1900-mid2020 02 2 An overview of earthquake and seismic-wave mechanics 2.1 Stress 2.2 Strain and rotation 2.3 Hooke's law 2.3.1 Elastic potential energy 2.4 Earthquakes: conceptual models 2.4.1 Elastic rebound 2.4.2 Rock friction and frictional sliding 2.4.3 Anelastic processes and postseismic relaxation 2.4.4 Earthquake scaling relations & stress drop 2.4.5 Stress drop, particle velocity, and rupture velocity 2.5 Seismic-waves: the elastic equations of motion 2.5.1 Harmonic motion 2.5.2 Seismic-wave attenuation Damped harmonic motion The quality factor, Q 2.5.3 Seismic wave attenuation in Earth 2.6 Summary 03 3 Earthquakes and plate tectonics 3.1 Divergent boundaries 3.2 Transcurrent boundaries 3.3 Convergent boundaries 3.3.1 Subduction zones 3.3.2 Continental collisions 3.4 Intraplate earthquakes 3.5 Summary 04 4 Earth motions & seismometry 4.1 Introduction 4.1.1 Seismic stations, networks, and arrays 4.2 Earthquake-related ground motions 4.3 Earth's continuous background motion 4.3.1 Ambient background motion power spectra 4.3.2 Power spectral density and time-domain ground motions 4.3.3 Horizontal and vertical ambient ground motions 4.3.4 Diurnal variation in ambient ground motions 4.3.5 Seasonal ambient ground motion variations 4.3.6 Reducing ambient motions in seismic data 4.4 Seismographic systems 4.4.1 Inertial pendulum seismometers 4.4.2 Electromagnetic seismographs 4.4.3 Digital recording and force-feedback sensors 4.5 Working with modern seismograms 4.5.1 Digital seismic recording systems 4.5.2 Removing instrument effects 4.5.3 Poles and zeros 4.5.4 Digital filters and signal decimation 4.5.5 Removing an instrument response by deconvolution 4.6 Seismometry's future 4.6.1 Seismometers everywhere 4.7 Summary 05 5 Seismogram interpretation and processing 5.1 Terminology for seismograms 5.2 Characteristics of body wave seismograms 5.2.1 Local, regional, and upper mantle 5.2.2 Teleseismic 5.3 Surface-waves 5.4 Travel-time curves 5.5 Signal processing basics 5.5.1 Time representation of seismic signals 5.5.2 Frequency-domain representation of seismic signals 5.5.3 Convolution 5.6 Picking arrival times 5.7 Summary 06 6 An introduction to earthquake location 6.1 Seismic arrival times 6.1.1 Seismic travel-time curves 6.2 Earthquake location with information from a single station 6.2.1 Inferring seismic source properties from seismogram characteristics 6.2.2 Inferring station-to-source distance & origin time using arrival times 6.2.3 Inferring station-to-source direction using ground motion polarization 6.3 Earthquake location with information from a seismic network 6.3.1 Epicenter estimation with tS - tP measurements 6.3.2 Origin-time estimation with Wadati diagrams 6.3.3 Refining locations using arrival-time residuals 6.4 Earthquake location as an inverse problem 6.4.1 A least-squares optimal location estimate 6.4.2 Halfspace arrival-time partial derivatives A numerical location example 6.5 Relative earthquake location methods 6.5.1 Master-event methods 6.5.2 Joint epicenter/hypocenter determination methods 6.5.3 Double-difference methods 6.6 Summary 07 7 Earthquake size & descriptive earthquake statistics 7.1 The energy in seismic waves 7.2 Earthquake magnitude scales 7.2.1 Local magnitude (ML) 7.2.2 Body-wave magnitude 7.2.3 Surface-wave magnitude (MS) 7.2.4 Other magnitude scales Regional magnitude, mb(Lg) Seismic coda magnitude 7.2.5 Magnitude saturation 7.3 Seismic energy, magnitude, and moment magnitude 7.4 Descriptive earthquake statistics 7.4.1 The Gutenberg-Richter relationship 7.4.2 Earthquake occurrence rates 7.5 Patterns in earthquake sequences 7.5.1 Foreshock patterns and earthquake nucleation 7.5.2 Aftershock patterns and rupture area 7.6 Earthquake catalogs 7.6.1 Modern earthquake catalogs 7.7 Summary 08 8 Earthquake prediction, forecasting, & early warning 8.1 The earthquake cycle 8.2 Paleoseismology 8.3 Earthquake prediction 8.3.1 Long-term deformation and earthquake migration patterns 8.3.2 Precursory phenomena 8.4 Earthquake forecasting and hazard estimation 8.5 Earthquake interactions and triggering 8.5.1 Static triggering 8.5.2 Dynamic triggering 8.5.3 Other triggering 8.6 Earthquake early warning 8.7 Summary 09 9 Tsunami and tsunami warning 9.1 Tsunami excitation 9.2 Tsunami propagation 9.3 Tsunami observation and monitoring 9.3.1 Onshore tsunami measurements 9.4 Tsunami forecasting and warning 9.5 Summary 10 10 Earth structure 10.1 Global Earth structure 10.2 Crustal structure 10.3 Upper-mantle structure 10.3.1 Discontinuities and anisotropy 10.4 Upper mantle heterogeneity 10.5 Lower-mantle structure 10.6 Structure of the core 10.7 Summary 11 11 Elasticity and seismic waves 11.1 Deformation, deformation gradients, and strain 11.1.1 Displacement gradients, strain, and rotation Normal strains Shear strains Rigid-body rotation 11.2 Stress 11.2.1 The stress tensor 11.2.2 Cauchy's relation Representative absolute stresses within Earth 11.2.3 The conservation of linear momentum - the equations of equilibrium 11.2.4 Conservation of angular momentum stress tensor symmetry 11.2.5 Principal stresses Tensors and tensor rotation 11.3 The equation of motion 11.3.1 Hooke's law and linear elasticity Isotropic elastic materials Elastic moduli and parameters 11.3.2 The equations of motion for linearly elastic materials 11.4 Wave equations for P- and S-wave potentials 11.4.1 The one-dimensional wave equation and solutions General solutions of the 1D wave equation Harmonic solutions of the 1D wave equation An approximate solution for an inhomogeneous 1D medium 11.4.2 Three-dimensional wave solutions Plane-wave phase and wavenumber vectors P- and S-wave displacements Wave polarization on seismograms 11.5 Seismic-wave speeds in Earth materials 12 12 Body waves and ray theory - travel times 12.1 Wavefronts and rays 12.2 The Eikonal equations and seismic rays 12.3 Travel times in media with depth-dependent properties 12.3.1 The seismic ray parameter (horizontal slowness) 12.3.2 Ray-path curvature 12.3.3 Distance and travel-time formulas 12.3.4 Travel-time curves for continuous media 12.4 Travel times in spherical Earth models 12.4.1 Travel-time expressions for spherical Earth models 12.5 Travel times in layered Earth models The layer-over-a-halfspace model Hidden layers and blind zones 12.6 Body-wave travel-time tables 13 13 Body-waves and ray theory - amplitudes 13.1 Geometric spreading in vertically varying media 13.2 Geometric spreading in spherical Earth models 13.2.1 Seismic-wave energy and amplitude 13.3 Body-wave attenuation 13.3.1 The standard-linear-solid attenuation model 13.3.2 Estimating Q in the seismic band 13.4 Seismic-wave reflection & transmission across geologic boundaries 13.4.1 P-waves at a fluid-fluid boundary Reflection variation with incidence angle / slowness 13.4.2 SH-waves at a solid-solid boundary 13.4.3 P- & S-waves at a solid-solid boundary 13.4.4 P- & S-waves at a solid-fluid boundary 13.4.5 P-S-wave reflection at a free surface The free-surface receiver functions 13.5 Body-wave energy flux factors 14 14 Surface waves 14.1 Halfspace Rayleigh waves 14.1.1 Halfspace Rayleigh-wave speed 14.1.2 Halfspace Rayleigh-wave displacements A Poisson solid Surface-wave geometric spreading 14.2 Love waves in a layer over a halfspace 14.3 Dispersion 14.3.1 Discrete dispersion 14.3.2 Continuous dispersion 14.3.3 Calculating group velocity 14.4 Dispersion on seismograms 14.4.1 Measuring dispersion Group-velocity estimation Phase-velocity estimation 14.4.2 Surface-wave dispersion and shallow Earth structure 14.5 Surface waves on a sphere 14.6 Surface-wave amplitude and attenuation 14.6.1 Geometric spreading 14.6.2 Attenuation 15 15 Free oscillations 15.1 A vibrating string 15.2 A vibrating sphere 15.3 Earth's free oscillations 15.3.1 Observing Earth's natural frequencies of vibration Mode splitting Mode coupling 15.4 Attenuation of free oscillations 15.5 Building models of Earth's interior using normal modes 16 16 Seismic point-source models 16.1 An ideal explosion 16.2 Faulting sources 16.2.1 Shear-faulting nomenclature 16.3 Earthquake P-wave "first motions" 16.4 Equivalent body forces for seismic sources 16.4.1 Seismic point-force sources 16.4.2 An ideal explosion 16.4.3 An ideal earthquake 16.4.3.1 Equivalent body force system non-uniqueness 16.5 Seismic moment tensors 16.5.1 Moment tensors and shear faulting Shear-faulting moment tensors in principle-axis coordinates Computing fault-normal and slip vectors from a moment tensor Computing seismic moment from a moment tensor 16.5.2 Non-double-couple seismic sources Moment-tensor decompositions 17 17 Seismic point-source radiation patterns 17.1 Elastostatics 17.1.1 Static displacement field due to a single force 17.1.2 Static displacement field due to a force couple 17.1.3 Static displacement field due to a double couple 17.2 Elastodynamics 17.2.1 Elastodynamic point-force displacements 17.2.2 Elastodynamic single-couple displacements 17.2.3 Moment-tensor radiation patterns 17.2.4 Elastodynamic double-couple displacements 17.3 Double-couple radiation patterns in geographic coordinates 17.3.1 Body-waves 17.3.2 Surface-waves 17.4 Estimating faulting geometry 17.4.1 P-wave first motion modeling 18 18 Earthquake rupture and source time functions 18.1 Rock fracture and fault rupture Earthquake rupture dynamics 18.1.1 Simple moment-rate function shapes 18.2 The one-dimensional Haskell source model 18.2.1 Rupture directivity 18.3 Seismic source spectra 18.3.1 Simple earthquake spectra models 18.3.2 Earthquake self similarity 18.4 Earthquake-slip heterogeneity 18.5 Source-spectrum estimation 18.5.1 Source-spectrum estimation 18.6 Source-time function estimation 18.6.1 Body waves 18.6.2 Surface waves Empirical Green's functions 19 19 Imaging seismic-sources 19.1 Body waveform modeling - a point source 19.1.1 Fundamental fault responses 19.1.2 Teleseismic body-wave modeling 19.1.3 Moment-tensor inversion 19.1.4 Time-dependent moment-tensor inversion 19.2 Surface-wave modeling for the seismic source 19.3 Global centroid moment-tensor solutions 19.4 Iterative sub-event identification 19.5 Earthquake finite-fault models 20 20 Imaging Earth's interior 20.1 Earth structure estimation using travel times 20.1.1 Herglotz-Wiechert inversion 20.1.2 Seismic traveltime tomography 20.1.3 Amplitude attenuation tomography 20.1.4 Surface-wave dispersion tomography 20.2 Discrete geophysical inversion 20.2.1 Surface-wave dispersion modeling 20.3 Earth structure estimation using seismic amplitudes and waveforms 20.3.1 P-wave receiver-function modeling 20.4 Full seismogram inversion 21 Bibliography 22 Index