The 2020 M7.6 Sand Point Alaska Earthquake: Slip Model, Stress Change Contributions and Tsunami Implications
On October 19, 2020 the M7.6 Sand Point strike-slip earthquake ruptured near the boundary between the Shumagin and Semidi segments of the Alaska-Aleutian megathrust at about 28 km depth. Thought to be an intra-slab event, the Sand Point earthquake is considered an aftershock of the July, 12 2020 M7.8 Simeonof megathrust earthquake that ruptured the deep part of the Shumagin seismic gap. An intriguing feature of the Sand Point event is the tsunami it generated, which is substantially larger than those produced by either the Simeonof event or the 2021 M8.2 Chignik earthquake; the latter ruptured the megathrust east of the Simeonof event.
Here we use high-rate GNSS and teleseismic waveforms, static GNSS offsets and InSAR observations to create a slip model for the Sand Point earthquake. We test scenarios that include only strike-slip faulting and others that also allow slip on the megathrust. Preliminary analysis suggests that coseismic GNSS offsets and teleseismic waveforms prefer a dominantly strike-slip scenario. Coulomb stress changes estimated for this scenario on the megathrust around the 2021 Chignik rupture zone are negligible, suggesting the Sand Point event did not significantly contribute to the timing of the 2021 Chignik event. We further compare observed tsunami waveforms to model predictions from various slip scenarios to investigate which coseismic model results in larger observed tsunami waveforms while maintaining a predominant strike-slip rupture mode and whether complex bathymetry or submarine landslides need to be invoked to explain the observed tsunami.
Session: Insights from Earthquakes in and Around Alaska in the 20 Years Since the Denali Fault Earthquake [Poster]
Type: Poster
Room: Evergreen Ballroom
Date: 4/21/2022
Presentation Time: 08:00 AM Pacific
Presenting Author: Revathy M. Parameswaran
Student Presenter: No
Additional Authors
Ronni Grapenthin Corresponding Author rgrapenthin@alaska.edu Geophysical Institute of the University of Alaska Fairbanks |
Julie Elliott julieelliott.ak@gmail.com Michigan State University |
Zhuohui Xiao zhhxiao@whu.edu.cn Wuhan University |
Revathy Parameswaran Presenting Author rmparameswaran@alaska.edu University of Alaska Fairbanks |
Jeffrey Freymueller freymuel@msu.edu Michigan State University |
Elena Suleimani ensuleimani@alaska.edu University of Alaska Fairbanks |
Dmitry Nicolsky djnicolsky@alaska.edu University of Alaska Fairbanks |
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The 2020 M7.6 Sand Point Alaska Earthquake: Slip Model, Stress Change Contributions and Tsunami Implications
Category
Insights from Earthquakes in and Around Alaska in the 20 Years Since the Denali Fault Earthquake
Description