There have been more than 150 tremors during the past 24 hours stretching from the Alberni Valley to Cowichan. (Photo John Cassidy and pnsn.org)

More than 150 tremors hit Vancouver Island in last 24 hours

Seismologists monitor to see if pressure will be added to major fault

More than 150 tremors have hit Vancouver Island in the last 24 hours, and seismologists are monitoring the situation to see if it turns into an Episodic Tremor and Slip event.

Vancouver Island is normally moving toward the Lower Mainland at a rate of about one centimetre per year.

“Ferry fares keep going up but the distance is actually getting a little bit shorter,” jokes John Cassidy, seismologist with the Geological Survey of Canada.

But every 14 months or so there is a Tremor and Slip event – a discovery made by two local scientists Gary Rogers and Herb Dragert – when Vancouver Island slips backwards a few millimetres towards Japan. Seismic recording instruments show Victoria moving in one direction and then changing direction for about two weeks during these episodes. These events add pressure to the locked Cascadian Subduction Zone fault.

“It involves tiny tremors that we can record. They are not earthquakes. People don’t feel these shaking events. But we can easily record them over many seismic stations at the same time,” said Cassidy. “It looks like a train or a rumbling.”

You can see the energy building up slowly and then dropping off slowly, says Cassidy. It’s not a typical earthquake signature. It’s more of a rumbling vibration sort of signal.

The tremors are recorded and mapped out, to show where the slip is taking place. It helps to identify the locked portion of the subduction fault where all the energy is being stored for future earthquakes.

“This is a really important piece of information to help us understand the subduction zone where these big earthquakes are more likely to occur,” said Cassidy. “It doesn’t help us predict when an earthquake will occur, though.”

Due to the fact that Episodic Tremor and Slip events give a slight nudge to a locked fault, it is a period of slightly higher hazard but Cassidy assures that it is not a huge change.

“It is similar to driving in slightly heavier traffic than you normally would. There might be slightly more risk,” said Cassidy. “Bottom line is that we live in a subduction zone where earthquakes can happen at any time. These tremors are a reminder to us that we do live in an active zone and to be prepared.”

It will take a week of monitoring the situation to see if a slip takes place.


 

keri.coles@oakbaynews.com

Follow us on Instagram
Like us on Facebook and follow us on Twitter.

Just Posted

Greater Victoria teachers experienced more than 30 incidents of violence from students in one month

Shuttered behavioural programs, lack of resources creates challenges for local schools

Esquimalt High robotics team heads to international competition

The Esquimalt Atom Smashers will participate in the FIRST Robotics Canada competition

Canadian alcohol policy gets failing grade from UVic researchers

Canadian provinces and territories collectively achieved less than half of their potential to reduce alcohol related harm

Island playoffs underway at Oak Bay High

Home team vies for fifth straight Island title

Black Press readers share photos of their favourite critters on #LoveYourPetDay

Greater Victoria is raining cats and dogs…and snails and goats

POLL: Will you be wearing pink to take a stand against bullying

Schools and workplaces across Greater Victoria and around the province will be… Continue reading

UPDATE: Man charged in stabbing of woman, off-duty cop outside B.C. elementary school

Manoj George, 49, is facing two counts of aggravated assault and two counts of assault with a weapon after the incident on Wednesday, Feb. 20.

Federal fisheries minister calls for precautionary approach to fish farming

Government still reviewing Federal Court’s decision on PRV – Wilkinson

Why do zebras have stripes? Perhaps to dazzle away flies

Researchers from University of Bristol look into why zebras have stripes

Poll: More voters believe Canada doing worse under Trudeau government

22 per cent believed the country is doing better and 27 per cent said things are the same

HBC shuttering Home Outfitters across Canada

North America’s oldest retailer is revamping its various stores to improve profitability

BC SPCA investigates Okanagan woman with prior animal abuse convictions

BC SPCA is investigating a property near Vernon

Man wanted for sex trafficking, confinement may be heading to B.C.

Kevin Myrthil, 26, is also accused of assault on a 19-year-old woman at an Edmonton hotel

Most Read