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A Re-Evaulation of Slip During the 2021 M8.2 Chignik, Alaska Earthquake

Description: 

Along the Alaska-Aleutian subduction zone, there have been more large earthquakes during the past century than at any other subduction zone, including four large M7+ earthquakes since 2020. The largest among these is the 2021 M8.2 Chignik earthquake, which ruptured part of the Semidi segment. This rupture started just to the east of a transition from lower to higher coupling on the megathrust. The Chignik earthquake has raised questions about earthquake triggering, relationships between coupling and earthquake rupture, and possible loading of the shallow megathrust. To answer these questions, a robust understanding of the coseismic slip distribution is needed. Multiple coseismic models have been published, but they show variations in the amplitude and location of slip. To improve our picture of the coseismic slip distribution, we will present new coseismic models of the 2021 Chignik earthquake that incorporate a larger dataset, including campaign GNSS measurements, and use two different slab models to test the influence of slab geometry.

The campaign GNSS measurements have been corrected for post-seismic afterslip with existing InSAR data that has been tied with static GNSS offsets, high rate GNSS data, and teleseismic waveforms. To test how different slab models affect slip estimates, we develop models that use both Slab2 and an interface model based on active source seismic imaging (ALEUT model). At intermediate depths of the megathrust, where the Chignik earthquake occurred, the ALEUT model suggests a plate interface several kilometers deeper than the Slab2 model, which coincides with the USGS hypocenter depth.

Session: Structure and Behavior of the Alaska-Aleutian Subduction Zone [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Anthony

Student Presenter: Yes

Invited Presentation: 

Authors