British Columbians may have been woken up by an earthquake early Monday morning that struck between Vancouver Island and Washington state.
The seismic event hit 42 kilometres east of Sidney, B.C., at 5:02 a.m. near the U.S. San Juan Islands at a depth of 17 kilometres.
Earthquakes Canada initially registered the quake at a magnitude of 4.6 but later adjusted it to 4.1.
The shaking was “lightly felt” around Victoria and Vancouver, officials say. Thousands of reports from people feeling the rattling have come in to the Earthquakes Canada website from as far as Chilliwack and Whistler, as well as along the Vancouver Island coast as north as Courtenay.
Emergency Management Minister Kelly Greene told CTV News the quake wasn’t large enough to trigger an early warning alert—an issue that came up earlier this month when some people reported not receiving an alert, or their phones going off well after an earthquake finished.
Read more: Why did only some people in B.C. get an earthquake alert? Federal agency explains
“Just woke me up,” Vancouver city councillor Peter Meiszner wrote on social media just after 5 a.m. “Shook my building pretty good in downtown Vancouver.”
There have been no reports of damage so far and there is no tsunami threat to B.C.
The City of Vancouver told CTV News, “given the magnitude and intensity of this earthquake were below thresholds at which Natural Resources Canada deems harm might be expected, no assessments of city bridges, infrastructure or roadways are currently planned” and the Ministry of Transportation said the same applies for provincial highways and transit.
There’s now a high-tech monitoring system in place for major bridges in the region, with the Structural Health Monitoring network operating sensors on 14 bridges that “collect real-time structural data to monitor the impact of seismic events,” according to a ministry statement.
Brent Ward, an earth sciences professor at Simon Fraser University, told CTV News damage would be expected if a magnitude five or higher quake hit near a populated area, and a magnitude six would constitute a “significant event.”
The quake is the third that could be felt in southwestern B.C. in recent weeks, following a 4.7 magnitude tremor near Sechelt the afternoon of Feb. 21 and a 3.8 quake near Victoria on Feb. 13.
Ward said it’s uncommon for there to be a string of earthquakes felt by so many people, but it’s not a cause for concern.
“We do live in a seismically active area. We get lots of earthquakes – just sometimes you get a period where ones are in areas where people can feel them,” he said, adding B.C. gets earthquakes almost every day but they’re too small to feel or are far away from population centres.
Monday’s earthquake was geologically similar to the one on the Sunshine Coast that shook homes across the region a little under two weeks ago—a shallow crustal earthquake on the North American plate.
Ward explained the Juan de Fuca plate is subducting under the North American plate where it’s locked and building up pressure.
“Every so often that stress builds up enough that it actually causes rocks to break, and that breaking or rupturing of the rock along a fault releases that energy in the form of seismic waves, and those waves travel through the earth and when they intersect the surface people may feel the ground shake,” he said.
Asked whether this quake would relieve enough pressure to prevent a big crustal event in the future, Ward said, “No, not at all.” He explained that the subduction zone is still locked and the stress is still building—but rest assured, he says Monday’s tremor didn’t make the chances of a big earthquake higher either.
When it comes to how prepared B.C. is for a larger quake, Ward said the province is doing fairly well. “We’re working really hard, there’s lots of seismic upgrading that’s happening to critical infrastructure,” he said, referencing updating schools and rebuilding St. Paul’s Hospital. He added B.C. has a “very robust” building code and anything built in the last 20 to 30 years should fare well in an earthquake.
“We’re doing all the right things. It’s just a question of how much money and resources can be put into it given our present financial situation,” he said. “We need to be cautious against downgrading earthquake spending.”
Greene said the event is another reminder to be prepared for a major quake, which essentially could happen any minute, or not for decades or even hundreds of years.
That includes having supplies to shelter in place for days as well as a grab-and-go bag in the case of evacuation, as well as knowing what to do when the ground starts shaking.
Read more: What should I do during an earthquake?
With files form CTV Vancouver’s Penny Daflos
