"Holocene Surface Rupture History of an Active Forearc Fault Redefines Seismic Hazard in Southwestern British Columbia, Canada" by K. D. Morell

Article

Holocene Surface Rupture History of an Active Forearc Fault Redefines Seismic Hazard in Southwestern British Columbia, Canada

Geophysical Research Letters (2018)

K. D. Morell, University of California, Santa Barbara
K. D. Morell, University of Victoria
C. Regalla, Boston University
C. Amos, Western Washington University
S. Bennett, United States Geological Survey
L. Leonard, University of Victoria
A. Graham, University of Victoria
T. Reedy, University of Nevada, Reno
V. Levson, University of Victoria
A. Telka, Paleotec Services Ottawa Ontario Canada

Link

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).

Keywords

Forearc faulting,
Paleoseismic trenching,
Seismic hazard

Disciplines

Geology and
Geophysics and Seismology

Publication Date

November 16, 2018

DOI

10.1029/2018GL078711

Citation Information

Morell, K.D., C. Regalla, C.B. Amos, S.E.K. Bennett, L. Leonard, A. Graham, T. Reedy†, V. Levson, and A. Tekla (2018) Holocene surface rupture history of an active forearc fault redefines seismic hazard in southwestern British Columbia, Canada, Geophysical Research Letters, 45 (21) 11,605-11,611, doi: 10.1029/2018GL078711.