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Megathrust complexity delimited the up-dip extent of slip during the 2021 Chignik, Alaska Peninsula earthquake

Authors

Liu,  Chengli
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Bai,  Yefei
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Lay,  Thorne
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Feng,  Yashan
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Xiong,  Xiong
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

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Citation

Liu, C., Bai, Y., Lay, T., Feng, Y., Xiong, X. (2023): Megathrust complexity delimited the up-dip extent of slip during the 2021 Chignik, Alaska Peninsula earthquake, XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) (Berlin 2023).
https://doi.org/10.57757/IUGG23-1186


Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5017407
Abstract
The up-dip extent of slip during large megathrust earthquakes is important for both tsunami excitation and subsequent tsunami earthquake potential, but it is unclear whether frictional properties and/or fault structure determine the up-dip limit. A finite-fault slip model for the 2021 MW 8.2 Chignik, Alaska Peninsula earthquake obtained by joint inversion and modeling of geodetic, seismic, and tsunami observations provides unusually good constraints on the up-dip edge of the slip. Rupture initiated ~35 km deep and propagated unilaterally northeastward with large-slip (up to 8.4 m) distributed over a depth range of 26 to 42 km beneath the continental shelf. Aftershocks concentrate up-dip of the coseismic slip around a strong megathrust reflector with high Coulomb stress change. The ~25 km deep up-dip edge of slip strongly correlates with a change in plate interface reflectivity apparent in reflection profiles, indicating that a structural and frictional transition provided a barrier to shallower rupture.