Upper Plate Structure and Megathrust Properties in the Shumagin Gap Near the July 2020 M7.8 Simeonof Event

Donna J. Shillington, Anne Bécel, Mladen R. Nedimović

Research output: Contribution to journalLetterpeer-review

2 Scopus citations

Abstract

Subduction zone architecture and properties are thought to control megathrust slip behavior, but few constraints on crustal structure and megathrust properties are available at sufficient resolution and depth, hindering understanding of linkages between structure and behavior. Here we present a P-wave seismic velocity model based on wide-angle seismic data integrated with collocated reflection imaging in the weakly coupled Shumagin Gap in the Alaska subduction zone, where a M7.8 occurred in July 2020. We show that this earthquake occurred near and below the Moho of the overriding plate where the megathrust is characterized by a 3- to 5-km-thick reflection band interpreted to represent tectonic mixing. The rheological heterogeneity of the plate boundary near and below the Moho could account for abundant interplate seismicity, repeated M7.x events, and patchiness of the 2020 rupture. Velocity variations in the overriding continental crust imply changes in rigidity that could further influence megathrust slip.

Original languageEnglish (US)
Article numbere2021GL096974
JournalGeophysical Research Letters
Volume49
Issue number2
DOIs
StatePublished - Jan 28 2022

Keywords

  • Alaska subduction zone
  • marine seismic data
  • megathrust
  • Shumagin Gap

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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