*Surface fault ruptures, *Radar interferometry, *Interferometry, *Global Positioning System, *Remote-sensing images, *Modulus of rigidity, *Space-based radar

This paper presents a new model of seismic rupture surface for the Chignik Mw 8.2 earthquake which occurred off the Alaska Peninsula on July 29, 2021. The model is based on data on surface displacements obtained by satellite radar interferometry from Sentinel-1A and 1B images and on horizontal GPS displacements in the area of this earthquake. We used satellite radar images for the period between July 17 and August 10, 2021, as well as GPS data for the period between July 18 and August 8, 2021. All of these displacements include both coseismic movements and some postseismic displacements. The rupture surface model was developed using F. Pollitz' solution to the problem concerning the displacement field at the surface of a spherical radially stratified planet due to a rectangular rupture inside the planet. The inversion was regularized by requiring that the direction of displacement at each element of the rupture plane be close to a specified direction as given by seismological data. The seismic rupture surface in this model is fitted by a plane extending for 225 km along strike and 126 km along dip, and which is subdivided into 48 identical elements. According to the model derived here, the type of displacement is a nearly pure thrust, with the displacement in general involving all of the rupture zone. The maximum slip was 5.7 m, with the mean slip as averaged over the entire rupture plane being 2.2 m. Assuming the shear modulus to be 32 GPa, we found the seismic moment based on the parameters of the plane we have derived and on the displacements on it as 1.95 × 1021 N m (Мw = 8.13), which is near the USGS and GCMT estimates based on seismological data. [ABSTRACT FROM AUTHOR]

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