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Title: Effects of depth of fault slip and continental shelf geometry on the generation of anomalously long-period tsunami by the July 2020 Mw 7.8 Shumagin (Alaska) earthquake
Authors: Mulia, IE
Heidarzadeh, M
Satake, K
Keywords: tsunami;Shumagin;Alaska-Aleutian;Long-period waves;Inversion;Extreme event
Issue Date: 31-Jan-2022
Publisher: Geophysical Research Letters
Citation: Mulia. I.E., Heidarzadeh. M. and Satake. K. (2022) 'Effects of depth of fault slip and continental shelf geometry on the generation of anomalously long-period tsunami by the July 2020 Mw 7.8 Shumagin (Alaska) earthquake', Geophysical Research Letters, 49 (3), pp. 1 - 10. doi: 10.1029/2021GL094937.
Abstract: Copyright © 2022 The Author(s) and American Geophysical Union. The July 2020 Mw 7.8 Shumagin earthquake occurred in the seismic gap region along the Aleutian subduction zone. This interplate earthquake generated a small tsunami, but with unusual long-period waves ranging between 40 and 90 min. We examined the cause of such an anomalous ocean wave through a source modeling inverted from tsunami and geodetic data. Our model indicates that the plate-boundary rupture area was confined at depths of 20–40 km, although the slip resolvability decreases with depth. The coseismic seafloor displacement predominantly took place on the shallow continental shelf. Therefore, the initial water surface displacement at a mean water depth of ∼200 m is responsible for the long-period waves, because tsunami period is inversely proportional to the square root of water depth. Furthermore, tsunami modeling implies that slip shallower than 20 km depth in the Aleutians would displace the seafloor beyond the continental shelf and generate shorter tsunami periods.
Description: Data Availability Statement: The tide gauge data for Sand Point ( and Dutch Harbor ( are provided by the Sea Level Station Monitoring Facility of the Intergovernmental Oceanographic Commission of the United Nations. The DART data of the United States National Oceanic and Atmospheric Administration's were downloaded from Static GNSS displacements were obtained from the UNAVCO Bulletin Board ( Bathymetric data are based on GEBCO 2020 Grid available at All figures were produced using the GMT software (Wessel & Smith, 1991).
ISSN: 0094-8276
Other Identifiers: e2021GL094937
Appears in Collections:Dept of Mechanical and Aerospace Engineering Research Papers

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