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

K. D. Morell, C. Regalla, C. Amos, S. Bennett, L. Leonard, A. Graham, T. Reedy, V. Levson, A. Telka

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

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).

Original languageEnglish (US)
Pages (from-to)11,605-11,611
JournalGeophysical Research Letters
Volume45
Issue number21
DOIs
StatePublished - Nov 16 2018
Externally publishedYes

Keywords

  • forearc faulting
  • paleoseismic trenching
  • seismic hazard

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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