OKANAGAN - Several recent earthquakes felt in the Okanagan could be mother nature’s way of segueing into The Great Shakeout Earthquake Drill which is coming up on Oct. 20.
Earthquakes Canada seismologist John Cassidy says there have been a few “felt” earthquakes in the Okanagan over the past few months but nothing truly unusual.
This 2.0 magnitude quake this morning, Oct. 12, about seven kilometres northwest of Penticton, was felt in that city, Kelowna and Okanagan Falls. It was 10 times less powerful than one that struck the area a month ago, Cassidy says.
The magnitude 4.0 event southeast of Penticton on Sept. 10 was larger than most Okanagan earthquakes but even that was below the threshold where damage might be expected.
“If you are close to the epicentre of a magnitude 4.0, there could be some frightening shaking,” he says.
Cassidy says there have been a three or four quakes in the Okanagan in the past couple of months, including a magnitude 3.0 near Princeton on Aug 15.
On average over a 15 year period, Cassidy says the Penticton area experiences around 12 quakes annually, based on statistics evaluating the number of earthquakes within 100 kilometres of the city over that time frame.
Sixty-two of those were in magnitude 2.0 range, while six were in the magnitude 3.0 range. Two have been magnitude 4.0.
“We do see low level seismic activity throughout the Okanagan. The biggest quake in recent times was a 4.5 event near Vernon in 1935 that cracked plaster, knocked dishes off shelves and broke a few chimneys,” he says, noting at that magnitude one would expect damage.
Cassidy says the region does feel earthquakes emanating from coastal B.C. and Washington State, noting the 2001 6.8 magnitude quake near Seattle and the 1946 7.2 quake that rumbled across Vancouver Island were both felt in the Okanagan. He says stresses from the moving Pacific tectonic plate are often transferred to the North American plate, sometimes activating old faults in the Okanagan.
In pioneer times, an earthquake estimated in the magnitude 6.5-7 range, originating near Colville, Washington, caused damage in the Osoyoos and Keremeos areas. Cassidy says it has only been recently scientists have discovered the fault that caused that quake, after searching for it for decades.
He adds the recent cluster of quakes is not necessarily a sign of “the big one” but rather a reminder that earthquakes do happen in the area and that it’s a good idea to be prepared.
Natural Resources Canada’s Earthquake website has information on earthquakes in the area and how to be prepared.
The Great ShakeOut, billed as the largest earthquake drill in the world, takes place Oct. 20. See the Great ShakeOut website for more information and to register.
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