Abstract

This dissertation utilizes multiple methods of earthquake detection, relocation, and characterization to investigate the patterns of seismicity along the Alaska subduction zone and Antarctica. The studies of the Alaska subduction zone are built on the data collected during the Alaska Amphibious Community Seismic Experiment (AACSE) that deployed temporary land and ocean-bottom seismometers along the Alaska Peninsula and offshore regions from May 2018 to September 2019. Using seismic arrivals at those stations, as well as a combination of other land-based networks, I relocated 1307 earthquakes in the incoming plate and trench slope regions of the Alaska subduction zone with an absolute relocation technique that included a 3-D seismic velocity model. Most of the earthquakes are within 50 km of the trench in the Shumagin segment, which is consistent with the mapped locations of plate-bending faulting. I also determined the focal mechanisms of 7 earthquakes on the incoming plate using first-motion polarities of the seismic arrivals. Normal faulting earthquakes predominate the Shumagin segment, which supports the cause of the faulting as plate bending before subduction. These results suggest elevated hydration of the incoming plate in the Shumagin segment compared to other areas along strike, as well as greater potential for large, tsunamigenic earthquakes in the outer rise. In another study, I propose a new rupture scenario for the 2018 Mw 7.9 Offshore Kodiak Earthquake that occurred 300 km southeast of Kodiak Island on the incoming plate. I relocate 500 aftershocks from the 2018 Mw7.9 Offshore Kodiak Earthquake using a relative relocation technique that solves for the location of the center of all of the events and the locations of events from that center. The locations of the events indicate three main north-south clusters of events, with the central cluster including the mainshock. There are many other, smaller north-south clusters of events interspersed between the main clusters, highlighting a southwest to northeast trend of en echelon-style faulting. High-resolution bathymetry and sub-bottom profiles show north-south faulting is pervasive across the aftershock region, with offsets in the subsurface reflectors indicating these faults have slipped repeatedly. I also find that the Coulomb stress increased along north-south faults from the mainshock rupture when modeling the stress change. I propose a new rupture scenario for the 2018 Mw 7.9 Offshore Kodiak Earthquake wherein many north-south en echelon faults ruptured following the mainshock. In the final study, I create a catalog of regional seismicity across sparsely-instrumented regions of Antarctica using a novel, deep-neural-network-based phase picker (autopicker). Existing catalogs of seismicity across Antarctica miss large regions that are distant from seismic stations. I train a new autopicker focused on regional arrival detection with manually-reviewed, high-quality seismic arrivals at Antarctica stations. I find 4246 events for 5 years, 2009-2013, of data. The seismicity is mostly concentrated in the Transantarctic Mountains, Marie Byrd Land, the Gamburtsev Mountains, and around coastal glaciers like Thwaites and Totten. These areas are prone to several seismic sources, including tectonic faulting, volcanism, and glacial movement. My catalog covers most of Antarctica and indicates promise in expanding the work to more years of data.

Committee Chair

Douglas Wiens

Committee Members

Joseph Guinness; Michael Wysession; Philip Skemer; Viatcheslav Solomatov

Degree

Doctor of Philosophy (PhD)

Author's Department

Earth & Planetary Sciences

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

11-6-2025

Language

English (en)

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