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Refining the Nature of Distributed and Localized Slip-Partitioning of the Totschunda-Fairweather to Denali Corridor Using Earthquake Relocations and Focal Mechanisms

Description: 

Southeastern Alaska and southwestern Yukon are at the plate boundary between the Pacific and North American plates and the Yakutat microplate. The region is undergoing complex active deformation due to the oblique collision of the Yakutat microplate with North America. Transpressional deformation is accommodated 300 km inboard from the plate boundary by large displacement, regional-scale faults, including the Fairweather, Denali, and Duke River fault systems. Monitoring in the region is limited due to the remote setting and year-round snow and glacial coverage. In the last decade, regional seismic networks have significantly expanded, leading to an increased density of stations largely attributed to the deployment of Transportable Array stations, many of which were converted to permanent stations in the Alaska regional network. In this study, we relocate more than 5,000 earthquakes between 2010 and 2021. These earthquake relocations show reduced uncertainty, particularly in depth, and allow us to show that brittle regime deformation occurs on a shallow fault network in the upper 10 km of the crust. The region has a shallow brittle-plastic transition consistent with elevated crustal temperatures across the Cordillera. We interpret and classify deformational kinematics across this corridor by combining earthquake relocations with regional focal mechanism solutions. The focal mechanism catalog includes 374 novel low-magnitude focal mechanism solutions. Our interpretive fault map includes the postulated Totschunda-Fairweather Connector fault, which helps to explain regional deformation. We identify new faults, such as the Kathleen Lake fault. Our interpretation includes a simplified conceptual model that describes the region characterized by transpression with distributed and localized slip partitioning. This study provides a current snapshot of active seismic deformation on a well-defined shallow network of faults occurring within this continually evolving oblique convergent tectonic regime.

Session: Cordilleran Strike-Slip Faults as Seismogenic and Seismological Features [Poster Session]

Type: Poster

Date: 5/2/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Katherine

Student Presenter: Yes

Invited Presentation: 

Authors