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

Unofficial holidays: Here’s what people are celebrating for the week of Sept. 20 to 26

Rabbit Day, Hobbit Day and One-Hit Wonder Day are all coming up this week

Port Hardy Mounties help First Nation chief build smokehouse

‘We have great maya’xala for all the community members, in each of the communities…’

Emaciated grizzly found dead on central B.C. coast as low salmon count sparks concern

Grizzly was found on Gwa’sala-‘Nakwaxda’xw territory in Smith Inlet, 60K north of Port Hardy

Access to remote Side Bay beach up in the bureaucratic air

Roads to the pristine north west coast Vancouver Island beach at risk of being deactivated

B.C. or Ontario? Residential school survivors fight move of court battle

It’s now up to Ontario’s Court of Appeal to sort out the venue question

Body discovered floating in water near Lasqueti Island

JRCC reports personnel aboard fishing vessel made the find

Young B.C. cancer survivor rides 105-km with Terry Fox’s brother

Jacob Bredenhof and Darrell Fox’s cycling trek raises almost $90,000 for cancer research

B.C. migrant, undocumented workers rally for permanent residency program

Rally is part of the Amnesty for Undocumented Workers Campaign led by the Migrant Workers Centre

Preparations underway for pandemic election in Saskatchewan and maybe B.C.

Administrators in B.C. and around the country are also looking to expand voting by mail during the pandemic

Nearly 20 per cent of COVID-19 infections among health-care workers by late July

WHO acknowledged the possibility that COVID-19 might be spread in the air under certain conditions

Ferry riders say lower fares are what’s most needed to improve service

Provincial government announces findings of public engagement process

Supreme Court Justice Ruth Bader Ginsburg dies at 87

The court’s second female justice, died Friday at her home in Washington

Comox Valley protesters send message over old-growth logging

Event in downtown Courtenay was part of wider event on Friday

Most Read