Earthquake relocations delineate discrete a fault network and deformation corridor throughout Southeast Alaska and Southwest Yukon

Tectonics
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Abstract

Deformation in southeastern Alaska and southwest Yukon is governed by the subduction and translation of the Pacific-Yakutat plates relative to the North American plate in the St. Elias region. Despite notable historical seismicity and major regional faults, studies of the region between the Fairweather and Denali faults are complicated by glacial coverage and the remote setting. In the last decade, significant improvements have been made to the density of regional broadband seismometer networks. We relocate more than 5,000 earthquakes between 2010 and 2021 in the region of southeastern Alaska and southwestern Yukon utilizing these improved seismic networks. With reductions in catalog uncertainty, particularly in depth, we quantify the thickness of the seismogenic layer in the crust throughout the region and locate seismicity on a shallow network of upper-crustal faults. Relocated earthquakes, combined with an updated focal-mechanism catalog, permit estimating and classifying motion of active faults. This includes mapping the Totschunda-Fairweather “Connector” fault, which plays an important role in explaining regional deformation, and identifying new faults like the Kathleen Lake fault. We draw similarities between our seismic observations and simplified conceptual models of regional tectonics, which describe a dominant transpressional regime and localized slip partitioning. Our results support a hypothesis where current deformation is taking place on a well-defined and evolved network of shallow faults in the corridor between the Totschunda-Fairweather “Connector” and Denali faults.

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Publication type Article
Publication Subtype Journal Article
Title Earthquake relocations delineate discrete a fault network and deformation corridor throughout Southeast Alaska and Southwest Yukon
Series title Tectonics
DOI 10.1029/2023TC008140
Volume 43
Issue 5
Year Published 2024
Language English
Publisher Americvan Geophysical Union
Contributing office(s) Geology, Geophysics, and Geochemistry Science Center
Description e2023TC008140, 15 p.
Country Canada, United States
State Alaska, Yukon
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