Holocene surface rupture history of an active forearc fault redefines seismic hazard in Southwestern British Columbia, Canada

Geophysical Research Letters
By: , and 

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Abstract

Characterizing the hazard associated with Quaternary‐active faults in the forearc crust of the northern Cascadia subduction zone has proven challenging due to historically low rates of seismicity, late Quaternary glacial scouring, and dense vegetation that often obscures fault‐related geomorphic features. We couple lidar topography with paleoseismic trenching across the Leech River Fault on southern Vancouver Island to produce the first detailed surface rupture history of an onland forearc fault in British Columbia, Canada. The results indicate that this fault produced three surface‐rupturing earthquakes in the last ∼9 kyr and is therefore capable of producing large (Mw>6) earthquakes in the future. We provide new constraints on the fault's length (∼130 km) and Holocene slip rate (≥0.2–0.3 mm/year) that, together with the earthquake ages, should be incorporated into new seismic hazard assessments and building code practices relevant to urban centers in southwestern British Columbia (Canada) and northwestern Washington State (United States).

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Holocene surface rupture history of an active forearc fault redefines seismic hazard in Southwestern British Columbia, Canada
Series title Geophysical Research Letters
DOI 10.1029/2018GL078711
Volume 45
Issue 21
Year Published 2019
Language English
Publisher American Geophysical Union
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 7 p.
First page 11605
Last page 11611
Country Canada
State British Columbia
Other Geospatial Leech River Fault, Vancouver Island