ABSTRACT

On 23 January 2018, the Mw 7.9 Gulf of Alaska earthquake occurred near the Aleutian subduction zone, where the devastating Mw 9.2 megathrust earthquake occurred in 1964. Such a large event can redistribute stress on nearby fault planes, which promotes failure and can perhaps trigger aseismic events. In this study, we use onshore Global Positioning System (GPS) data to retrieve coseismic ground deformation and to invert for the finite‐fault‐slip distribution on complex fault geometries. Complex fault geometries are initially determined by applying constraints such as the aftershock distribution and backprojection imaging, followed by fitting the GPS observations. We model the Gulf of Alaska earthquake as a rupture on an orthogonal conjugate fault system that contains four subfaults. We find that 71.6% of the total moment release occurred on two west‐southwest‐oriented fault planes. The Coulomb failure stress increased by up to 1.01±0.39  bar in the shallow portion of the eastern Aleutian subduction zone between 149° and 151° W. Mapping of stress changes from the 2018 Gulf of Alaska earthquake indicates a limited stress increase in the region of the 1964 Alaska earthquake.

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