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

EarthquakeTsunami

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

 

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

West Shore Rotary Club raises $20,000 with Golf Ball Drop fundraiser

Nearly 4,000 golf balls poured onto Olympic View golf course Saturday

Construction slows weekend traffic at Millstream overpass

West Shore RCMP recommend Leigh Road exit instead

TRAFFIC: Saanich emergency crews responding to Pat Bay Highway collision

Incident took place at Haliburton Road intersection

Saanich race car driver shifts gears as pandemic cuts U.S. season short

Bill Okell, 65, sets sights on Canadian racing circuit for 2020

Chorus expands online options to in-person rehearsal in Langford, Oak Bay

Free, non-auditioned SingYourJoy recruits those aged 16 to 29

B.C. records 98 more COVID-19 cases, most in Lower Mainland

One new senior home outbreak, Surrey Memorial outbreak over

POLL: Do you agree with the decision to call a provincial election for Oct. 24?

British Columbians will put their social distancing skills to the test when… Continue reading

Is it time to start thinking about greener ways to package cannabis?

Packaging suppliers are still figuring eco-friendly and affordable packaging options that fit the mandates of Cannabis Regulations

Join Black Press Media and Do Some Good

Pay it Forward program supports local businesses in their community giving

Vancouver Island Tour de Rock riders roll into Parksville Qualicum Beach

Saturday’s schedule includes Port Alberni, Ucluelet and Tofino, followed by Nanaimo on Sunday

97 distressed horses, cats and dogs seized from farm in Princeton

RCMP assisted as BC SPCA executed search warrant

$250K reward offered as investigation continues into Sea to Sky Gondola vandalism

Police also asking for specific footage of Sea to Sky highway around time of incident

Most Read