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Megathrust splay faults at the focus of the Prince William Sound asperity, Alaska

Journal of Geophysical Research

By:
, , , ,
DOI: 10.1002/jgrb.50372

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Abstract

High-resolution sparker and crustal-scale air gun seismic reflection data, coupled with repeat bathymetric surveys, document a region of repeated coseismic uplift on the portion of the Alaska subduction zone that ruptured in 1964. This area defines the western limit of Prince William Sound. Differencing of vintage and modern bathymetric surveys shows that the region of greatest uplift related to the 1964 Great Alaska earthquake was focused along a series of subparallel faults beneath Prince William Sound and the adjacent Gulf of Alaska shelf. Bathymetric differencing indicates that 12 m of coseismic uplift occurred along two faults that reached the seafloor as submarine terraces on the Cape Cleare bank southwest of Montague Island. Sparker seismic reflection data provide cumulative Holocene slip estimates as high as 9 mm/yr along a series of splay thrust faults within both the inner wedge and transition zone of the accretionary prism. Crustal seismic data show that these megathrust splay faults root separately into the subduction zone décollement. Splay fault divergence from this megathrust correlates with changes in midcrustal seismic velocity and magnetic susceptibility values, best explained by duplexing of the subducted Yakutat terrane rocks above Pacific plate rocks along the trailing edge of the Yakutat terrane. Although each splay fault is capable of independent motion, we conclude that the identified splay faults rupture in a similar pattern during successive megathrust earthquakes and that the region of greatest seismic coupling has remained consistent throughout the Holocene.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Megathrust splay faults at the focus of the Prince William Sound asperity, Alaska
Series title:
Journal of Geophysical Research
DOI:
10.1002/jgrb.50372
Volume
118
Year Published:
2013
Language:
English
Publisher:
American Geophysical Union
Contributing office(s):
Alaska Science Center Geology Minerals
Description:
14 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
5428
Last page:
5441
Country:
United States
State:
Alaska
Other Geospatial:
Prince William Sound