Unlike what would happen with the Big One, the two earthquakes most recently felt in southwest B.C. were on faults that ‘we either didn’t know about or didn’t know were active,’ says an expert from the University of Victoria. Just 10 days after a 4.7-magnitude quake struck 24 kilometres northeast of Sechelt, a similar-sized jolt occurred Monday at about 5 a.m. It was centred 42 km east of Sidney.
Initial reports had the quake at a magnitude of 4.6, but it was revised a short time later to 4.1, according to the Natural Resources Canada website. Emergency Info B.C. took to social media to say the quake was “lightly felt” around Vancouver and Victoria. There were no reports of damage, but many Postmedia reporters said the quake rattled them out of their sleep.
Is it normal to feel two earthquakes so close together?
Leonard, who has lived in the region since 2001, said it was unusual for two earthquakes that people could feel to occur in such quick succession. “These two that I’ve felt in the last 10 days are, I think, the strongest ones that I’ve felt in my whole time here,” she said. She said, as far as she’s aware, the last time there was a “cluster” of similar earthquakes was in the late 1990s.
But, given the seismic activity in the region, Leonard said having back-to-back earthquakes wasn’t unexpected.
Should we expect more earthquakes?
Leonard said there were a number of smaller aftershocks following the Monday morning earthquake. Such aftershocks should typically trail off over the next few days or weeks. “Unfortunately, there is no way to tell if there will be more earthquakes in the region in the near future,” she said.
Are they an indication that the “Big One” is coming?
“When we talk about the ‘Big One,’ we’re talking about an earthquake that happens every few hundred years, right on that boundary between the Juan de Fuca plate and the North America plate,” Leonard said. She said the two recent quakes occurred on different, shallower faults — approximately 15 kilometres deep — that exist in the crust of the North America plate. “We’re learning more and more about these faults in the area that we really knew very, very little about, even 10 years ago,” she said. The earthquakes that occurred Monday morning and on Feb. 21, “those are both on faults that we either didn’t know about or didn’t know were active,” she said. “There is no reason to think that changes in these stresses will trigger the next ‘Big One,’” she said. The last massive earthquake to hit the region was on Jan. 26, 1700.
