Ye, L., Lay, T., Kanamori, H., Yamazaki, Y. & Cheung, K. F. The 22 July 2020 M W 7.8 Shumagin seismic gap earthquake: Partial rupture of a weakly coupled megathrust. Earth Planet. Sci. Lett. 562, 116879 (2021).

Bai, Y., Liu, C., Lay, T., Cheung, K. F. & Ye, L. Optimizing a model of coseismic rupture for the 22 July 2020 M W 7.8 Simeonof earthquake by exploiting acute sensitivity of tsunami excitation across the shelf break. J. Geophys. Res.: Solid Earth 127, e2022JB024484 (2022). Horowitz, W. L., Steffy, D. A. & Hoose, P. J. Geologic report for the Shumagin Planning Area, Western Gulf of Alaska. (U.S. Department of the Interior, Minerals Manages Services, Alaska OCS Region, 1989). OCS Report, MMS 89-0097. Scholz, C. H. The Mechanics of Earthquakes and Faulting. 439 (Cambridge Univ. Press, New York, 1990).As seismic and geodetic data can provide complementary constraints on the rupture process, we used both data types to invert the rupture process of the 19 October 2020 event assuming first one and then two fault segments. We performed non-linear finite fault inversions 29, 30, involving the joint analysis of coseismic static offsets, hr-GNSS time series, and seismic waveforms. A simulated annealing algorithm was used to solve for the slip magnitude and direction, rise time, and average rupture velocity for subfaults on the two segments. For each parameter, we set specific search bounds and intervals. The subfault size is chosen as 5 km × 5 km, and the rake angles on the two fault segments are constrained to be right-lateral purely strike-slip and purely dip-slip, respectively. We allowed both the rise and fall intervals of the asymmetric slip rate function for each subfault to vary from 0.6 to 6.0 s; thus, the corresponding slip duration for each subfault is limited between 1.2 and 12 s. We let the slip vary from 0.0 to 8.0 m, and the average rupture velocity is allowed to vary from 0.5 to 3.0 km/s. Green’s functions for static displacements and seismic waveforms are computed using a 1-D layered velocity model 31. Equal weighting among the data functionals for GNSS statics and seismic waveforms was used in this study. Tsunami modeling Shillington, D. J., Bécel, A. & Nedimovíc, M. R. Upper plate structure and megathrust properties in the Shumagin Gap near the July 2020 M7.8 Simeonof event. Geophys. Res. Lett. 49, e2021GL096974 (2022). Niazi, M. & Chun, K. Y. Crustal structure in the southern Bering Shelf and the Alaska Peninsula from inversion of surface-wave dispersion data. Bull. Seism. Soc. Amer. 79, 1883–1893 (1989). Ye, L. et al. Rupture model for the 29 July 2021 M W 8.2 Chignik, Alaska earthquake constrained by seismic, geodetic, and tsunami observations. J. Geophys. Res.: Solid Earth 127, e2021JB023676 (2022). Bai, Y., Yamazaki, Y. & Cheung, K. F. Convergence of multi-layer nonhydrostatic models in relation to Boussinesq-type equations. J. Waterway Port Coastal Ocean Eng. 144, 06018001–06018001 (2018).

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