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

Victoria’s Royal Jubilee Hospital home to new cancer diagnostic suite

The Gordon Heys Family PET/CT Suite was unveiled at the BC Cancer Centre-Victoria

Unsealed record suggests U.S. man convicted in murder of Saanich couple left DNA on zip tie in 1987

William Talbott is set to be sentenced Wednesday in the murders of Jay Cook and Tanya Van Cuylenborg

Hatley Gardens at Royal Roads, now free to public

1,500 plants recorded in garden, including 1,000-year-old Douglas Fir

Supreme Court Judge rules medicinal marijuana company must vacate farm in Central Saanich

Evergreen Medicinal Supply Inc must vacate no later than Aug. 31, 2019

Studies for E&N corridor still on track after BC Transit investments

Recent investment in bus fleet expansion doesn’t slow studies into alternative transportation routes

Surrey court clerk files human rights complaint related to concussion

Deborah A. Ryane claims her employer discriminated against her on basis of mental disability

Food fight: Liberals, Tories trade shots as pre-campaign battles intensify

Health Canada released an overhauled document that did away with traditional food groups and portion sizes

Okanagan Air Cadet challenges gender-exclusive haircut policy

Haircut regulation inspires challenge around gender identity

VIDEO: Bystander training gains traction as tool to prevent sexual harassment, violence

Julia Gartley was sexually assaulted after an event, and no one stepped in to help

Sexual assaults, extortion on the rise even as crime rates stay low: Stats Canada

Rates of police-reported sexual assault rose for the fourth year in a row

Vancouver Island teens missing after vehicle found ablaze near Dease Lake, BC

RCMP say a body discovered nearby not one of the missing teens

A year later, ceremony commemorates victims of the Danforth shooting

It’s the one-year anniversary of when a man opened fire along the bustling street before shooting and killing himself

Most Read