Rupture Model for the 29 July 2021 M W 8.2 Chignik, Alaska Earthquake Constrained by Seismic, Geodetic, and Tsunami Observations

A great earthquake struck the Semidi segment of the plate boundary along the Alaska Peninsula on 29 July 2021, re‐rupturing part of the 1938 rupture zone. The 2021 M W 8.2 Chignik earthquake occurred just northeast of the 22 July 2020 M W 7.8 Simeonof earthquake, with little slip overlap. Analysis of teleseismic P and SH waves, regional Global Navigation Satellite System (GNSS) displacements, and near‐field and far‐field tsunami observations provides a good resolution of the 2021 rupture process. During ∼60‐s long faulting, the slip was nonuniformly distributed along the megathrust over depths from 32 to 40 km, with up to ∼12.9‐m slip in an ∼170‐km‐long patch. The 40–45 km down‐dip limit of slip is well constrained by GNSS observations along the Alaska Peninsula. Tsunami observations preclude significant slip from extending to depths