Study identifies new active earthquake fault line in Saanich

Study identifies new active earthquake fault line in Saanich

Earthquake geologist and University of Victoria PhD candidate Theron Finley describes where an active fault line runs through a residential neighbourhood in Saanich.

“Just where that van is going down the hill right now, we’re a couple of metres higher than the road that continues on the other side there. That van just crossed the fault essentially,” he says.

The fault line runs through the area at a 45-degree angle.

Finley points to the far end of Elk Lake, and says the fault line likely starts at Saanich Inlet, then runs all the way under the lake, then across the Pat Bay Highway onto Cordova Bay.

“We have evidence of an earthquake that happened on this fault line sometime between 2.3-and 4.7 thousand years ago. In geological time frame, that’s very recent, and we consider that to be an active fault,” Finley says.

Using Lidar Animation, the computer program maps a region, then removes all structures on the surfaces, including trees and buildings, giving scientists a clear view of fault lines – including the one through Elk Lake.

Two years ago, scientists dug a trench next to the lake to see where the layers of sediment have moved.

Radiocarbon dating determined when the last earthquake took place, with a likely magnitude anywhere from 6.1 to 7.6.

Dr. John Cassidy, earthquake seimologist with Natural Resources Canada, says the discovery will help improve earthquake hazard preperation in the region.

“It’s really exciting. It gives us a better idea of where potentially the active faults are located in this region,” he says. “It wasn’t identified previous to this research. So it uses the latest technology, the latest information, combining a number of different methods to identify this fault that has likely seen one earthquake in the past 10,000 years.”

The information gathered here will enable officials to fold it into other studies, but also put into practical uses, such as updating the national building code.

“Folks should take this as a motivation to do, prepare your earthquake [kits], and increase your own resiliency in any way you can,” Finley says.

Even though this fault line is regarded as active, an earthquake from this fault line is not likely anytime soon. But it’s a timely reminder that we live in an earthquake zone.

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Mary GriffinMary Griffin

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