Modeling of Earthquake Ground Motion: From the Source to the Site.

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Date

2024-08-07

Authors

Nye, Tara

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Publisher

University of Oregon

Abstract

This dissertation investigates different approaches for improving modeling ofearthquake ground motion by focusing efforts on the different physical properties which are traditionally thought to contribute to shaking–– the source, the path, and the site. The robustness and informativeness of earthquake simulations and empirically-derived ground motion models rely on accurate modeling of these different components. Methods to improve ground motion modeling are highly studied; however, due to the complexity of processes that contribute to shaking intensities and uncertainty, much is still left poorly understood, especially when modeling rare or atypical events. This dissertation utilizes both simulated and real earthquake data to better constrain source, path, and site parameters. In this dissertation, we use a one-dimensional semistochastic model to simulate data for the 2010M7.8 Mentawai tsunami earthquake, as well as for 112 moderate-to-large arbitrary Cascadia Subduction Zone (CSZ) events. Tsunami earthquakes and CSZ ruptures are scarce, which results in minimal data to analyze and thus a poorer understanding of the rupture physics. However, a future occurrence of either scenario is likely to result in significant damage. With the paucity of real data, simulations are necessary to train and test earthquake and tsunami early warning algorithms. We use near-field observed data from the Mentawai tsunami earthquake to ascertain source parameter values needed to simulate tsunami earthquake-type events. With the absence of recordings from a CSZ interface event, we use global ground motion and scaling models to validate and tune modeling of the source and path in the simulation model. Through our analyses, we find the simulations to be well-modeled and representative of these uncommon events. Finally, we constrain site effects in the seismically-active San Francisco Bay Area (SFBA) by using real recordings of small-to-moderate earthquakes to estimate the high frequency attenuation parameter (κ) and its site contribution (κ0). We develop an automated algorithm for selecting the frequency bounds used to estimate κ, and we find spatial trends in κ0 to be consistent with regional anelastic attenuation models and shallow geology. Through ground motion analyses, we find κ0 to reasonably model regional ground motion and is thus a valuable contribution to future ground motion studies in the SFBA. This dissertation includes previously published and unpublished co-authored material.

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Keywords

Earthquake Simulations, Ground-Motion Modeling, Seismology

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