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.

EarthquakeTremors

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Cowichan residents can Climb for Alzheimer’s in their own backyard

for the first time ever, open to anyone, anywhere in the province

Battle of Fairy Creek: blockade launched to save Vancouver Island old-growth

‘Forest Defenders’ occupy road to prevent logging company from reaching Port Renfrew-area watershed

B.C. records 30-50 new COVID-19 cases a day over weekend, no new deaths

Many of those testing positive were identified by contact tracing for being linked to other confirmed infections

Five B.C. First Nations call out Canada for ‘discriminatory’ food fish practices

West Coast nations say government ignoring court-won right to chinook and coho

Rent-relief program becomes new front in fight between Liberals, opposition

Opposition trying to draw parallels between decision to have Canada Mortgage and Housing Corp. run program and the WE controversy

Nanaimo woman will buy ‘supersonic’ hair dryer after $500,000 lotto win

Debra Allen won $500,000 in July 28 Lotto Max draw

Ottawa sets minimum unemployment rate at 13.1% for EI calculation

Statistics Canada says the unemployment rate was 10.9 per cent in July

Cougar euthanized after attacking little dog in Qualicum area

Owner freed pet by whacking big cat, but dog didn’t survive the attack

$45K in donations received after couple’s sudden death in Tulameen

Sarah MacDermid, 31, and Casey Bussiere, 37, died August long weekend

Most Read