Officials are closely watching an earthquake swarm off the coast of Vancouver Island, where a 6.4 magnitude earthquake was recorded on Thursday.
John Cassidy, an earthquake seismologist with Natural Resources Canada, told Global News that since July 3 there have been a few hundred earthquakes in that area with most registering between three and five magnitudes.
“It’s a very active region,” he said.
“It’s a really complicated, tectonic setting. It’s where oceanic plates are being formed and being pushed towards North America. But there are also faults in that region where these tectonic plates slide past one another, which looks like what today’s earthquake and most of the other swarm earthquakes have been occurring.”
Cassidy said Thursday’s 6.4 magnitude earthquake was about 200 km off the coast of Tofino so while it was a large quake, the distance created a buffer for people living on the west coast of Vancouver Island.
“There’s sort of a horizontal slipping of one plate past another one,” Cassidy said.
“So because it’s that horizontal motion, we generally don’t see tsunamis generated by that type of movement or that type of an earthquake. But there have been a few hundred events over the past week.”
Cassidy added that aftershocks were expected from Thursday’s earthquake and those will continue over the coming days.
He expects the earthquake swarm to stop in the next few days or week.
“These earthquakes are not connected to faults or the subduction fault in any way,” he said.
“So we wouldn’t expect any link between these offshore events and other earthquakes that happen closer to land. So these don’t tell us that we’re any closer to a bigger earthquake or that a bigger earthquake is less likely or more likely.”
Cassidy said this is an active earthquake region and large earthquakes have happened in the past.
In 1918, a 7-magnitude earthquake was recorded beneath Vancouver Island and a 7.3-magnitude earthquake was recorded beneath the island in 1946.
A 7.8 earthquake has also been recorded off the coast of Haida Gwaii.
“Large earthquakes happen here, and they will happen again in the future,” Cassidy said.
“We don’t know when, but the research that we do is really aimed at understanding what we can expect in terms of ground shaking during future earthquakes, whether those earthquakes are tomorrow or in 10 years or in 50 years.”
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