Crustal structure of the Alaska subduction zone across the 2021 m8.2 Chignik earthquake rupture area from wide-angle seismic data

Burstein, Joshua Alexander (2023) Crustal structure of the Alaska subduction zone across the 2021 m8.2 Chignik earthquake rupture area from wide-angle seismic data. Masters thesis, Northern Arizona University.

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Abstract

Understanding the influence of large-scale crustal structure on megathrust slip behavior is essential for evaluating seismic and tsunami hazards at convergent plate margins. The subduction zone offshore of the Alaskan Peninsula is an excellent area to examine controls on subduction zone behavior because it has experienced a sequence of recent large earthquakes and it exhibits dramatic along-strike variability in seismicity and geodetic locking. The incoming sediments and oceanic plate in this region have been cited as factors controlling variability in megathrust slip behavior, but the influence of the overriding continental plate is less well studied. Here we focus on the Semidi segment of the Alaska subduction zone, which is strongly locked and regularly ruptures in great (M>8) megathrust earthquakes, including the July 2021 M8.2 Chignik earthquake. We present a two-dimensional P-wave seismic velocity model along a ~365-km-long profile obtained by joint reflection-refraction tomographic inversion of wide-angle seismic (WAS) data collected in 2011 aboard the R/V Marcus G. Langseth. Model uncertainty was estimated using a Monte Carlo approach. The resulting P-wave velocity model displays large-scale velocity variations in the overriding plate that constrain the extent of the accretionary prism and accreted crustal terranes that form the overriding plate: the Prince William and Chugach terranes. Shallow slow slip and afterslip are focused beneath the accretionary prism and younger, lower velocity Prince William Terrane while rupture in the 2021 earthquake is concentrated below the higher velocity Chugach terrane, suggesting that the upper plate influences slip behavior here.

Item Type:	Thesis (Masters)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	alaska; earthquake; megathrust; semidi; subduction zone; wide-angle seismic
Subjects:	Q Science > QE Geology
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > School of Earth Sciences and Environmental Sustainability
Date Deposited:	24 Oct 2025 17:47
Last Modified:	24 Oct 2025 17:47
URI:	https://openknowledge.nau.edu/id/eprint/6280

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