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Gabriel Gribler

November 20, 2019 @ 3:00 pm - 5:00 pm MST

Dissertation Information

Title: Rayleigh Wave Analysis in the Presence of High Impedance Boundaries

Program: Doctor of Philosophy in Geophysics

Advisor: Dr. Dylan Mikesell, Geosciences

Committee Members: Dr. Lee Liberty, Geosciences, Dr. Jack Pelton, Geosciences, and Dr. Jodi Mead, Mathematics

Abstract:

Surface wave data is commonly used to estimate shear wave velocity of the subsurface. Most standard approaches for analyzing surface wave data fail under conditions when high-impedance boundaries, or sharp contrasts, exists within the range of sensitivities. I present two primary scenarios, one with a high velocity bedrock layer in the upper 20 meters overlain by low velocity unconsolidated sediment, and a thin high velocity road layer on top of unconsolidated sediments. For the shallow bedrock case, I present new multicomponent methods to more accurately and reliably extract surface wave dispersion information from active source waveforms. I also present a new data inversion method that utilizes additional information from multicomponent wavefields, allowing for more accurate estimates of shear wave velocities in these environments. For the thin, high velocity surface layer, I highlight the potential pitfalls of ignoring this layer when inverting for the underlying shear wave velocities, and I propose a solution that yields more accurate velocity estimates. All of these approaches are explained and presented using modeled data, then extended to highlight the improvements over standard approaches using real data.