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

Iyan E. Mulia, Mohammad Heidarzadeh, Kenji Satake

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10 Citations (SciVal)

Abstract

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.

Original languageEnglish
Article numbere2021GL094937
JournalGeophysical Research Letters
Volume49
Issue number3
Early online date31 Jan 2022
DOIs
Publication statusPublished - 16 Feb 2022

Bibliographical note

Funding Information:
The work is part of the RIKEN Pioneering Project “Prediction for Science.” M. Heidarzadeh is funded by the Royal Society (The United Kingdom), Grant No. CHL\R1\180173.

Funding Information:
The work is part of the RIKEN Pioneering Project ?Prediction for Science.? M. Heidarzadeh is funded by the Royal Society (The United Kingdom), Grant No. CHL\R1\180173.

Publisher Copyright:
© 2022. American Geophysical Union. All Rights Reserved.

Keywords

  • Alaska-Aleutian
  • extreme event
  • inversion
  • long-period waves
  • Shumagin
  • tsunami

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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