A map showing earthquakes and the various tectonic plates around the Pacific Ocean. (Nick Murray/News Staff)

Vancouver Island overdue for the big one, can also expect mega-thrust tsunami

The last big earthquake was 70 years ago in Courtenay

According to seismologists, Vancouver Island is overdue for a magnitude 7 earthquake and has entered a period of time where an additional magnitude 9 mega-thrust rupture earthquake, likely to cause a tsunami, can be expected.

“In our part of the world, there are the big Pacific and North American [tectonic] plates, and caught in-between the two is the Juan de Fuca plate system,” says Taimi Mulder, seismologist at the Geological Survey of Canada (GSC), which monitors all seismic activity in Western Canada.

ALSO READ: Scientists warn warmer and more acidic oceans threaten marine life

Over millions of years, these plates push and grind under and past each other in areas called subduction zones. Earthquakes are caused and can be tiny or they can be massive, like the 2004 Sumatran earthquake, which ruptured 1,000 kilometres of coastline.

“An earthquake is like ringing a bell. The earthquake is the clapper that sets it off and the bell reverberates,” said Mulder. “In an earthquake, energy is sent shooting in all directions and it pings around inside the earth making the whole earth vibrate.”

Magnitude 4 or 5 earthquakes will likely wake you up, while a 7 will result in toppled bookcases and fallen chimneys. Thanks to B.C.’s stringent building code, structural collapse is not expected in magnitude 7s. Magnitude 8 or 9s have the same severity of shaking as a 7, but their duration lasts longer, often over 2 or 3 minutes. They cause structural building damage and ruptured gas lines, often causing fire.

The last big Vancouver Island earthquake struck Courtenay in 1946 and measured 7.3 on the Richter scale. The GSC says quakes of this magnitude should happen every decade, so the Island is about 70 years overdue.

ALSO READ: Hundreds of floating ‘Sponge Bobs’ help track ocean currents

As well as this imminent quake, Mulder says we have entered the timeframe to expect a magnitude 9 mega-thrust rupture earthquake too. These Cascadia Subduction Zone earthquakes happen every 200 to 800 years, and the last one occurred 300 years ago. If it hits magnitude 9, it will cause a tsunami, wreaking havoc on some coastal communities on the Island.

While storms often whip up 100 or 200 metres worth of surface water, tsunamis move the whole water column, several kilometres of water, at over 700 km/h, close to the speed of a jetplane.

The GSC collaborates with the nearby Institute of Ocean Sciences (IOS), whose world-class programmers and super computers model tsunami effects.

“We have the ability to simulate different earthquake scenarios,” says IOS acting manager of ocean sciences division Jon Chamberlain. “What type of wave it would likely generate, the likely maximum size of wave and how long it would take to reach certain parts of the coastline.”

ALSO READ: BC Ferries’ marine super talks dodging whales

Mulder explains one such scenario, “The wave that will hit the west coast is likely to be about 10m high, wrapping around the Island and being 4 or 5m by the time it hits Victoria, 1 or 2m when it reaches Vancouver.”

West coast residents will most likely receive hours of notice for tsunamis originating from across the Pacific, but only 15–45 minutes for those from the Cascadia Subduction Zone. There will be more time for people in Greater Victoria. Mulder advises that if a quake lasts longer than three minutes, it is likely magnitude 9 and a tsunami is incoming.



nick.murray@peninsulanewsreview.com

Like us on Facebook and follow us on Twitter

 

A computer system that records seismological data in real-time, from instruments around the coast and in the sea. (Nick Murray/News Staff)

A map showing every western B.C. earthquake of the last 20 years in a glass display case. (Nick Murray/News Staff)

Earthquake seismologist Taimi Mulder of the Geological Survey of Canada explains plate tectonics. (Nick Murray/News Staff)

Just Posted

Graffiti Days 2019 a huge success

Hundreds of cars and spectators — including a History channel TV personality — turned out for the event

Bus company fears for future if another licence issued for Interior routes

Adventure Charters waiting to see if Ebus BC is approved for Prince George-Kamloops run

Sea Cadets wind up another year with Ceremonial Review

Corps is fundraising for a trip to Halifax, Nova Scotia in 2020

WorkBC helping break down barriers to employment

Office offers a wide range of services to help people find sustainable careers

Local News Briefs: Get garden ideas with Ashcroft tour

The Rivertown Players are back, invasive plant management, reduced tipping fees, and more

VIDEO: Acknowledging skeptics, finance minister vows to build Trans Mountain project

Bill Morneau said he recognizes ‘huge amount of anxiety’ in Calgary over future of oil and gas sector

Home care for B.C.’s elderly is too expensive and falls short: watchdog

Report says seniors must pay $8,800 a year for daily visits under provincial home support program

B.C. ‘struggling’ to meet needs of vulnerable youth in contracted care: auditor

Auditor general says youth in contracted residential services may not be getting support they need

Pair of B.C. cities crack Ashley Madison’s ‘Infidelity Hotlist’

Data from the website reveals Abbotsford and Kelowna hottest spots for cheaters

Life’s work of talented B.C. sculptor leads to leukemia

Former Salmon Arm resident warns of dangers of chemical contact

Billboard posted along B.C.’s Highway of Tears to remember missing and murdered Indigenous women

Billboards featuring Indigenous artwork to be placed in Surrey, Kamloops and near Prince George

Federal cabinet ministers visit Edmonton, Calgary, in wake of TMX approval

Natural Resources Minister Amarjeet Sohi is set to visit Trans Mountain Corp.’s terminal in Edmonton

B.C. municipality prepares to forbid overnight camping by homeless despite court ruling

While courts have ruled against blanket bans, Langley City is employing a site-by-site approach

B.C. auditor says Indigenous grad rate highest ever but education gaps exist

The percentage of Indigenous students graduating from B.C. public high schools has hit its highest level ever

Most Read