A megathrust earthquake hit South Vancouver Island 320 years ago on Jan. 26, 1700. While scientists encourage preparation, they say the 320-year mark doesn’t mean another earthquake is necessarily imminent. (Black Press File Photo)

320 years since the ‘Big One’ doesn’t mean it’s overdue: B.C. professor

‘It could happen today, tomorrow or 100 years from now’

Next month marks 320 years since the Cascadia Megathrust earthquake rocked the B.C. coast, shooting a tsunami wave at the speed of a jumbo jet across the Pacific Ocean to Japan.

The impact was recorded overseas and left a historically viable marker of what was likely one of the most catastrophic natural events in region’s history.

READ ALSO: POLL: When do you think the next major earthquake will hit Vancouver Island?

READ ALSO: B.C. has history of big earthquakes

While the threat of the ‘Big One’ is a quiet source of concern for many – a looming, abstract dread behind calls for seismic infrastructure upgrades, earthquake safety awareness and regular ‘ShakeOuts’ in schools and offices across the region – the next megathrust is not necessarily overdue.

“We can’t predict earthquakes and we are a million miles away from being able to,” says Edwin Nissen, University of Victoria professor and Canada Research Chair in geophysics. Nissen has expertise in global geohazards including the subduction zones of the Cascadia plate boundary – the convergent boundary stretching from northern Vancouver Island to northern California.

“It’s wrong to say the next earthquake is overdue,” he says – pointing to the unpredictable pattern of plate shifts over history. “But it is correct to say it might happen tomorrow. It might happen today or tomorrow or in 100 years.”

READ ALSO: Be Prepared: Hospitals prep for mass casualties

The factors behind the next big quake are complicated, but boil down to the Cascadia subduction zone, where the oceanic plate is pushed below the continental lithosphere. Typically, the plates are stuck in that position, but when the oceanic plate slides deeper beneath the continental plate, an earthquake – and tsunami– is generated.

The estimated time between Cascadia subduction zone earthquakes is anywhere from 200 to 800 years. The last on record was Jan. 26, 1700.

That means another earthquake is neither impossible nor overdue, Nissen says.

“Prediction is probably impossible. Many of us think it will always be impossible, ” he says. “What we can do is forecast the location and magnitude – but instead of a [specific] time you give an interval of time and a probability.”

Nissen says research shows a 15 to 30 per cent chance of a major earthquake (magnitude 8 to 9) in the next 50 years, but that leaves an up to 70 per cent chance that there will be no earthquake at all – at least for the next five decades.

READ ALSO: Be Prepared: After the “Big One,” will your family be ready?

“Humans think over short time scales – we don’t think in decade or 100-year time spans,” Nissen says. “But for earthquake safety that’s the time span we need to think in.”

Nissen says infrastructure upgrades, emergency plans and advancing earthquake early warning technologies are all part of a necessary planning process – even if the next megathrust doesn’t hit until 2120.

Nissen quips, “If there was a 30 per cent chance of rain you would still bring an umbrella.”



nina.grossman@blackpress.ca

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

Surrey council sets new rules for Good Citizen of the Year award

Candidates have more hurdles to jump before getting nominated for the prestigious local title

EXPLORE SURREY: Tee up some adventures in the city

Also: A walk through Surrey’s public art collection

In honour of player killed in crash, Surrey soccer team becomes BB5 United

Brandon Bassi died a few months before CCB won the national title last fall

North Surrey rink to reopen first as part of city’s phased schedule for facilities

Councillor pushes for Surrey’s pools and aquatic centres to reopen this month

Canucks ride momentum into NHL playoff series against defending Stanley Cup champs

PREVIEW: Vancouver opens against St. Louis on Wednesday

Man, 54, charged in connection with fatal attack of Red Deer doctor

Doctor was killed in his walk-in clinic on Monday

One dead as fish boat sinks off southern Vancouver Island

Shawnigan Lake-registered Arctic Fox II went down off Cape Flattery, west of Victoria

42 more people test positive for COVID-19 in B.C.

The province has recorded no new deaths in recent days

Joe Biden selects California Sen. Kamala Harris as running mate

Harris and Biden plan to deliver remarks Wednesday in Wilmington

Displaced tenant ‘heartbroken’ to find Langley City condo robbed after fire

Wedding rings of Michelle Buchan’s have since been recovered, but much is still missing

‘Agitated’ man pulls out knife on 3 people in Abbotsford

Witnesses sought for incident on Monday night near city hall

FoodMesh taking its emergency food recovery project nationwide

Pilot project in Chilliwack helped show that food surpluses could be diverted to charities in need

Most Read