Date of Award

12-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Statement

Doctor of Philosophy in Geophysics

Department

Department of Geosciences

Committee Chair

Tape, Carl

Committee Member

Chow, Bryant

Committee Member

Modrak, Ryan

Committee Member

West, Michael

Committee Member

Abers, Geoffrey

Table of Contents

Chapter 1: General introduction

Chapter 2: Navigating the space of seismic anisotropy for crystal and whole-Earth scales

2.1 Abstract

2.2 Introduction 

2.3 Visualizing elastic maps and the distances among them

2.4 Applications to previous studies

2.4.1 Composition dependence of elastic symmetry

2.4.2 Pressure and temperature dependence of elastic symmetry

2.4.3 Rocks and subduction flow models for the upper mantle

2.5 Navigation within the space of elastic maps

2.6 Discussion

2.6.1 Laboratory measurements of minerals and rocks

2.6.2 Estimation at the laboratory scale

2.6.3 Prospects for seismic imaging

2.7 Conclusion

2.8 Acknowledgments

2.9 Data availability

2.10 References

2.11 Figures

Chapter 3: Toward full waveform inversion for homogeneous 21-parameter anisotropic materials

3.1 Abstract

3.2 Introduction

3.3 Introduction

3.4 Sensitivity kernels for exotic arrivals

3.5 Analysis of misfit functions

3.6 Full waveform inversion of homogeneous anisotropic blocks

3.7 Conclusion

3.8 Future opportunities

3.9 Open research

3.10 References

3.11 Tables

3.12 Figures

Chapter 4: Investigation of a tilted transversely isotropic model of Alaska using 3D seismic wavefield simulations

4.1 Abstract

4.2 Introduction

4.3 Background

4.4 Methods

4.4.1 Region

4.4.2 Earthquakes, data, and estimating source mechanisms

4.4.3 3D wavefield simulations

4.4.4 Preparing the TTI tomographic model

4.4.5 Reduction from TTI to HTI, VTI, and ISO

4.4.6 Measurements: timeshifts and differential timeshifts

4.5 Results

4.5.1 Original model: comparisons with data

4.5.2 Modified model

4.5.3 Visualization of waveform differences

4.5.4 The influence of reducing anisotropic complexity: synthetics vs data

4.5.5 The influence of reducing anisotropic complexity: synthetics vs synthetics 

4.6 Discussion

4.6.1 Workflow for validating general anisotropic tomographic models

4.6.2 Manual adjustments to tomographic models

4.6.3 The influence of different datasets and different tomographic approaches 

4.7 Conclusions

4.8 Future opportunities

4.9 Open research

4.10 References

4.11 Tables

4.12 Figures

Chapter 5: Software for computational seismology

5.1 Introduction

5.2 Software packages: development

5.3 Software packages: contributions

5.4 Software packages: user

5.5 Summary

5.6 Open research

5.7 References

Chapter 6: General conclusions

Abstract

Seismic anisotropy characterizes how elastic waves travel through solid materials with different speeds, depending on the direction of the waves and the direction of particle motion of the waves. Evidence of seismic anisotropy in the Earth is widespread, from seismic waves sampling the crust, mantle and even the core, to active-source, industry-scale seismic experiments, to laboratory mea­ surements of rock samples from boreholes or at the surface. Global models of the Earth provide a highly averaged image of anisotropy. Studies based on shear wave splitting measurements from local and global earthquakes indicate that the anisotropy in the Earth is much more complex, es­pecially within subduction zones. Only a limited number of studies have taken the extra step of quantifying the anisotropy within the Earth in terms of structural parameters. This calls for tools and methods to understand anisotropic elasticity at its foundation, its effects on seismic waveforms, and innovative techniques to solve for the elastic parameters when only waveform observables are provided. This dissertation employs three-dimensional anisotropic wavefield simulations to better understand the link between elastic parameters and variations in seismic waveforms. With three independent studies, this dissertation provides steps taken towards addressing the larger goal of quantifying anisotropy in the Earth from crystal to whole-Earth scales.

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