UVic geologist leads discovery of an active fault under Greater Victoria

University of Victoria geologist Kristin Morell has led the discovery of an active fault line that runs a few kilometres from downtown Victoria, including the Esquimalt Lagoon area and just offshore from James Bay and Clover Point.

The international study published this month discovered that the Leech River fault, previously believed to be inactive, has caused at least two major earthquakes since the last glaciation over 15,000 years ago. This makes the fault active and a potential hazard for the area. Information on the discovery was incorporated into the recent seismic vulnerability assessment commissioned by the City of Victoria.

Unlike the better-known Cascadia megathrust fault predicted to cause the earthquake referred to as the “Big One”—which is active every 300 to 500 years—crustal faults can display no detectable seismic activity for thousands of years, making them difficult to study. Instead, Morell and her team read the trail of clues that earthquakes leave behind long after they’ve ended. By looking at topographic features, they can see how past earthquakes shaped the area.

“Now that we’ve identified that the Leech River fault is active, the next step is for us to nail down exactly when and how big the most recent earthquakes were,” says Morell. The information can then be used to help with hazard mitigation and emergency response planning. “When we understand the risks posed, there’s a lot we can do to keep our communities safe.”

The study was featured this month in the Geological Society of America’s publication GSA Today. Contributors to the study included Lucinda Leonard and Vic Levson from UVic’s School of Earth and Ocean Sciences, as well as researchers from Boston University and Western Washington University. The study was supported by the Natural Sciences and Engineering Research Council and the National Science Foundation.

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