Tsunamigenic structures in a creeping section of the Alaska subduction zone

TitleTsunamigenic structures in a creeping section of the Alaska subduction zone
Publication TypeJournal Article
Year of Publication2017
AuthorsBécel, A, Shillington, DJ, Delescluse, M, Nedimović, MR, Abers, GA, Saffer, DM, Webb, SC, Keranen, KM, Roche, P-H, Li, J, Kuehn, H
JournalNature Geoscience
Volume10
Pagination609–613
ISSN1752-0908
KeywordsGeodynamics, Geology, Natural hazards, seismology, Tectonics
Abstract

Segments of subduction zones that are capable of generating tsunamigenic earthquakes appear to have characteristic structural configurations. These structures include heterogeneous plate interfaces, a small wedge of deformed sediment at the toe of the overriding plate (the frontal prism), and splay faults in the crust of the overriding plate that root within the plate boundary megathrust. Here we use seismic reflection imaging to show that these features also exist within a creeping segment of the Alaska subduction zone, the Shumagin Gap. We identify an active crustal-scale normal fault system that dips landward and resembles that involved in the 2011 Tohoku-oki earthquake in Japan. We also find that the Shumagin Gap has a small frontal prism, a deep-water splay fault, and that the plate interface here is rough and thinly sedimented. We propose that lateral propagation of rupture from a neighbouring segment into the Shumagin Gap may explain a tsunamigenic earthquake that occurred there in 1788 and that tsunamigenic potential should be considered in hazard assessments for the region. Our results demonstrate that structural configurations similar to those in Tohoku may exist in other subduction zones, including within creeping segments or segments with no record of historical megathrust earthquakes, but are under-recognized. Identifying similar configurations globally may improve our ability to anticipate regions capable of generating large tsunamis.

URLhttps://www.nature.com/articles/ngeo2990
DOI10.1038/ngeo2990

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