Little late Holocene strain accumulation and release on the Aleutian megathrust below the Shumagin Islands, Alaska

Geophysical Research Letters
By: , and 

Links

Abstract

Can a predominantly creeping segment of a subduction zone generate a great (M > 8) earthquake? Despite Russian accounts of strong shaking and high tsunamis in 1788, geodetic observations above the Aleutian megathrust indicate creeping subduction across the Shumagin Islands segment, a well-known seismic gap. Seeking evidence for prehistoric great earthquakes, we investigated Simeonof Island, the archipelago's easternmost island, and found no evidence for uplifted marine terraces or subsided shorelines. Instead, we found freshwater peat blanketing lowlands, and organic-rich silt and tephra draping higher glacially smoothed bedrock. Basal peat ages place glacier retreat prior to 10.4 ka and imply slowly rising (<0.2 m/ka) relative sea level since ~3.4 ka. Storms rather than tsunamis probably deposited thin, discontinuous deposits in coastal sites. If rupture of the megathrust beneath Simeonof Island produced great earthquakes in the late Holocene, then coseismic uplift or subsidence was too small (≤0.3 m) to perturb the onshore geologic record.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Little late Holocene strain accumulation and release on the Aleutian megathrust below the Shumagin Islands, Alaska
Series title Geophysical Research Letters
DOI 10.1002/2014GL059393
Volume 41
Issue 7
Year Published 2014
Language English
Publisher Wiley
Contributing office(s) Alaska Science Center Geology Minerals
Description 9 p.
First page 2359
Last page 2367
Country United States
State Alaska
Other Geospatial Shumagin Islands
Online Only (Y/N) N
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page