- This event has passed.
November 20, 2019 @ 3:00 pm - 5:00 pm MST
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
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.