Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust

Geophysical Research Letters
By: , and 

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Abstract

Current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust. Here we report geological evidence for large tsunamis, occurring on average every 300–340 years, near the source areas of the 1946 and 1957 Aleutian tsunamis. These areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate that the megathrust is currently creeping. At Sedanka Island, evidence for large tsunamis includes six sand sheets that blanket a lowland facing the Pacific Ocean, rise to 15 m above mean sea level, contain marine diatoms, cap terraces, adjoin evidence for scour, and date from the past 1700 years. The youngest sheet, and modern drift logs found as far as 800 m inland and >18 m elevation, likely record the 1957 tsunami. Modern creep on the megathrust coexists with previously unrecognized tsunami sources along this part of the Aleutian Subduction Zone.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust
Series title Geophysical Research Letters
DOI 10.1002/2015GL066083
Volume 43
Issue 1
Year Published 2016
Language English
Publisher American Geophysical Union
Contributing office(s) Alaska Science Center Geology Minerals
Description 9 p.
First page 76
Last page 84
Country United States
State Alaska
Other Geospatial Aleutian Islands
Online Only (Y/N) N
Additional Online Files (Y/N) N