Collaborative Research: The 2020-2021 Alaska-Aleutian Earthquake Sequence: Cascading Events & Stress Loading of the Shallow Megathrust

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Estimating the size and location of future earthquakes remains an elusive goal in seismology and hazard research. This project studies the 2020 M7.8 Simeonof and 2021 M8.2 Chignik earthquakes that ruptured adjacent portions of the deeper interface between the North American and Pacific Plates offshore Alaska. The project will probe the relationship between these two earthquakes: how the Earth’s response to the 2020 Simeonof event may have affected the fault area that failed in the 2021 Chignik earthquake, the role of tectonics and geometry of this plate interface in earthquake occurrence, and how these events fit in the longer history of earthquakes along this plate boundary. Another key question is whether the yet unruptured shallower parts of the plate interface in this region may rupture in earthquakes that have the potential to create devastating, Pacific-wide tsunamis. This project will deploy four GPS/GNSS instruments around the Chignik earthquake rupture to better capture deformation following the earthquake. This project is a collaboration between the University of Alaska, Fairbanks and Michigan State University.This project will study crustal motions and stress changes due to the Simeonof and Chignik earthquakes directly and from readjustments of the Earth after the earthquakes. It will make use of multiple geophysical data sources, including high-precision GPS instrumentation, combined with modeling of crustal motions and stress changes. Careful separation of different tectonic processes, and models of realistic fault geometries informed by accurate earthquake relocation will yield improved models for how the plates moved during and after the Chignik earthquake. Coupled with similar, separately generated products for Simeonof earthquake and the earlier 1938 M8.3 earthquake in the same region, the project will create short- and long-term stress change models, and investigate how stress change may influence future rupture patterns. A virtual workshop will bring together subduction zone scientists, generate interest in the data produced through this project, showcase new findings, and inspire novel science and future opportunities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.