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

Renovicted Prince Rupert tenants claim no where to go

Pinecrest tenant Jen Quick said landlord has not paid as per settlement agreement

Revving up for the ride

Prince Rupert Harley Riders 39th annual toy run wheeled in toys and donations

Pineridge students learn about Orange Shirt Day

Students and teachers wore orange shirts designed by a SD 52 student to commemorate Sept. 30

Haida hereditary chief is BC Liberal Candidate for North Coast Region

Roy Jones Jr. is named BC Liberal MLA candidate for the North Coast

B.C. salmon farms challenge activists’ demands for site closures

News reporting also unfair, inaccurate and distorted

B.C. counts 125 new COVID-19 cases, up to 1,284 active

No new deaths or health care facility outbreaks

B.C. VOTES 2020: Wilkinson to stop 24-hour camping in city parks

Ban on ‘unsafe roadside panhandling’ to be enforced

Lessons from a pandemic: How to design a nursing home that’s safe and love-filled

A look at how one care home is battling the pandemic with the social needs of the elderly in their care

B.C. salmon farm opponents demand answers from DFO

First Nations, conservation groups dismayed by omission of sea lice in risk assessments

Join Black Press Media and Do Some Good

Pay it Forward program supports local businesses in their community giving

Winter tires, chains now mandatory along most B.C. highways

Drivers without the proper winter tires – which must also be in good condition – can be fined $109

Health Canada green-lights rapid COVID-19 test

Health Canada approved the BCube test from Hyris Ltd. in the United Kingdom Sept. 23

First Nations Health Authority chief medical officer concerned with rising COVID-19 cases

“There’s still so much we don’t know and we’re learning everyday about this particular virus.”

FINLAYSON: COVID-related job losses concentrated in urban areas… especially Metro Vancouver

The biggest job losses, in absolute terms, have been in Metro Vancouver

Most Read