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

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

A display graphic showing the Cascadia Subduction Zone. (Nick Murray/News Staff)

Just Posted

Central Saanich changes incentives for housing developments

Changes shift incentives for some developments from development cost charges to building permit fees

VIDEO: Saanich resident shocked when trespasser licks security camera, rummages through mail

‘I found the situation really bizarre,’ said the Gordon Head resident

BC Ferries crew member taken to hospital after getting struck by bow doors

Two sailings between Horseshoe Bay and Departure Bay were cancelled

Bulk or boxed candy? Trick-or-treat maps help Canadian families prepare for Halloween

Census Mapper uses 2016 census data to predict busiest neighbourhoods

Black Press Media celebrates women who are making a difference

Helping others is the cornerstone of the work Shannon Drew does in… Continue reading

VIDEO: Explosion, fire sends woman running from Saanich home

Heavy smoke in the area, crews on scene

Jack’s Devils beat Quinn’s Canucks 1-0 in NHL brother battle

New Jersey youngster scores first career goal against Vancouver

Two charged after owner’s wild ride through Kamloops in his stolen truck

Crystal Rae Dorrington, 37, and Derrick Ronald Pearson, 32, facing multiple charges

Judge orders credit union’s bank records for Kelowna social worker facing theft allegations

The man is accused of negligence, breach of contract, fraud and a conspiracy with Interior Savings

Leaders pour it on with rallies, boosts for candidates as campaign reaches peak

The federal election campaign has reached a crescendo

Allegations of racism lead to ministry investigation at Vancouver private school

St. George’s School was contacted over what the school describes as ‘deeply offensive behaviour online’

Not a political question: Thunberg calls for climate action in Alberta

Edmonton police estimated the size of the crowd at about 4,000

Zantac, the over-the-counter heartburn drug, pulled in Canada, U.S.

Health Canada also investigates possible carcinogen in some ranitidine drugs

B.C. public safety minister says cannabis edibles not in stores til January

Mike Farnworth says he wants regional issues considered when it comes to licensing

Most Read