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

VIDEO: Giants take a 1-0 playoff series lead

Vancouver beat Seattle 7-1 in game one of the best-of-seven Western Conference series in Langley

Coroners office reports 29 fatal drug overdoses in Langley in 2018

Dealing with drug overdoses, fatal or not, creates serious stress for first responders.

PHOTOS: ‘Enchanted Forest’ excursion unveils Aldergrove park’s new Nature Discovery Area

Atop the former Aldergrove Lake now sits a large “free play” adventure area for kids.

Aldergrove team could return as all-stars on ‘The Amazing Race Canada’

Mother and daughter duo given a second chance, though their fate rests in the hands of voters

Stolen Bentley spotted going wrong way down highway found in Summerland

The car has been recorded going the wrong way on the Coquihalla, found two days later

Province announces $18.6 million for B.C. Search and Rescue

The funding, spread over three years, to pay for operations, equipment, and training

Vancouver-bound transit bus involved in fatal crash near Seattle

One man was killed and a woman injured in crash with bus purchased by TransLink

Late-season wave of the flu makes its round in B.C.

BC Centre for Disease Control reported 50 per cent jump in flu cases in first weeks of March

Tofino’s housing crisis causing some to seek shelter at the local hospital

Tofino’s housing crisis is pushing the town’s ‘hidden homeless’ population into the forefront.

Sentencing judge in Broncos crash calls for carnage on highways to end

Judge Inez Cardinal sentenced Jaskirat Singh Sidhu to eight years

2 fires in Victoria caused by cigarettes prompts warning from deputy fire chief

Two separate fires caused by cigarette butts were avoidable

Most Read