Paleoseismic study of the XEOLXELEK–Elk Lake fault: A newly identified Holocene fault in thenorthern Cascadia forearc near Victoria, British Columbia, Canada

Nicolas Harrichhausen; Theron Finley; Kristin D. Morell; Christine Regalla; Scott E.K. Bennett; Lucinda J. Leonard; Edwin Nissen; Eleanor McLeod; Emerson M. Lynch; Guy Salomon; Israporn Sethanant

USGS · 70259664

Paleoseismic study of the XEOLXELEK–Elk Lake fault: A newly identified Holocene fault in thenorthern Cascadia forearc near Victoria, British Columbia, Canada

Nicolas Harrichhausen·Theron Finley·Kristin D. Morell·Christine Regalla·Scott E.K. Bennett·Lucinda J. Leonard·Edwin Nissen·Eleanor McLeod·Emerson M. Lynch·Guy Salomon·Israporn Sethanant

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Abstract

High-resolution topographic data show a tectonic scarp formed in Quaternary sediments near the city of Victoria in the northern Cascadia forearc on Vancouver Island, British Columbia, Canada. A paleoseismic trench excavation across the structure, the XEOLXELEK–Elk Lake fault, shows evidence for a Holocene (after 12.2 cal ka BP) surface-rupturing reverse-slip earthquake that produced a fault-propagation fold and resulted in the formation of a ∼1.4 to 3.5 m-high scarp. Fault-propagation fold modelling indicates ∼3.2 m of reverse slip on a 50°-dipping fault plane reproduces the observed deformation, and fault-scaling relations suggest a single earthquake rupture with this surface displacement could occur during a ∼Mw 6.1– 7.6 earthquake. Given the fault’s location within the metropolitan area of Victoria, an earthquake near this magnitude would result in significant damage to local infrastructure and this fault is worth considering in future seismic hazard assessments.

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Nicolas Harrichhausen, Theron Finley, Kristin D. Morell, Christine Regalla, Scott E.K. Bennett, Lucinda J. Leonard, Edwin Nissen, Eleanor McLeod, Emerson M. Lynch, Guy Salomon, Israporn Sethanant. 2022. Paleoseismic study of the XEOLXELEK–Elk Lake fault: A newly identified Holocene fault in thenorthern Cascadia forearc near Victoria, British Columbia, Canada. https://pubs.usgs.gov/publication/70259664

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