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.

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

Just Posted

‘We thought it was an earthquake,’ homeowners okay after tree falls

Mature tree falls on roof of Victoria Avenue house

Hydro pole fire closes portion of Metchosin Road in Colwood

Motorists are advised to avoid the area of Metchosin Road near Royal Bay

Saanich roads doused in more than 300 tonnes of salt during snowstorm

Crews cleared roads around the clock during the mid-January storm

Strong winds expected in Greater Victoria Friday evening

Winds are expected to ease Saturday morning

VIDEO: The Victoria byelection leads a selection of today’s news stories

A selection of Greater Victoria top stories for Jan. 17

Theft victim confronts suspects with baseball bat on Vancouver Island

RCMP in Nanaimo seek to identify of two people alleged to have used a stolen credit card

Closed mills, housing surge support a positive forecast for lumber industries

B.C. lumber producers have closed mills accounting for 18% of province’s capacity, RBC report says

Kelowna’s ‘Baby Mary’ finds biological parents after more than 30 years

Geneologist and DNA test helped her connect with her biological parents

Clerk bruised, traumatized after armed robbery at Nanaimo liquor store

Few details on male suspect in Wednesday incident, says Nanaimo RCMP

One last blast of winter tonight for parts of the Island before temperatures on the rise

A snowfall warning is in effect Friday including east Vancouver Island.

POLL: Has the recent snow had an impact on your daily life?

Old Man Winter had Greater Victoria in his icy grip this week.… Continue reading

Greater Victoria Crime Stoppers wanted list for the week of Jan. 14

Greater Victoria Crime Stoppers is seeking the public’s help in locating the… Continue reading

‘Scariest boat ride of my life’: Passengers trapped by ice on rocky B.C. ferry sailing

The Nimpkish docked in Bella Coola on Jan.12 coated in a thick layer of ice

Most Read