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BC tsunami would inundate coast

Andrea Stockton, staff writer

March 25, 2011 — 30 minutes. That's all the time it would take for a wave to inundate the coast of BC if an earthquake similar to the one that hit Japan rattled the region.

The areas in red are most at risk for seismic activity
The areas in red are most at risk for seismic activity

Canada's largest historic onshore earthquake hit central Vancouver Island on June 23, 1946. The deadly 7.3 magnitude quake was felt as far away as Prince Rupert, BC and Portland, Oregon.

While the damage was far less significant than the 9.0 magnitude earthquake that recently devastated Japan, the question remains:

What if the 'Big One' hits home?

If a quake similar to the one in Japan hits, a damaging outcome would be difficult to avoid, especially with the threat for a powerful tsunami on BC's coast.

“We would be looking at a tsunami at least as big as the one we saw in that terrifying video footage from Japan,” says Brent Ward, geologist at Simon Fraser University in BC. “It's been estimated that the wave would be 10 metres high in Port Alberni and there's a lot of places below that 10 metre mark.“

How long does that leave people to move to safety?

“People would probably have about 30 minutes after the earthquake to get to high ground before the wave inundated the coast.”

Ward adds that when an earthquake strikes, the flexure of the tectonic plates is what displaces the water soon after.

Tsunami of 1964. Courtesy: Alberni Valley Museum
Tsunami of 1964. Courtesy: Alberni Valley Museum

The last tsunami to hit the west coast was in 1964 and it pummeled the coastal town of Port Alberni.

“We do have a history in Port Alberni of three large waves that impacted that town after the 1964 Alaskan earthquake. They were extremely lucky because the first wave came in when the tide was quite low. It was observed by the RCMP. The Mills were actually on maintenance so there wasn't a night shift on and they were able to evacuate the majority of the people out of the low lying areas before the other waves came in because they came in on a rising tide,” explains Ward.

The community now has a tsunami siren warning system, which is the only one of its kind in BC.

Once a month, the city runs a test to warn people of what to do if a tsunami were to hit the coast. The warnings are broadcast over solar powered speakers, which prompts residents to move to higher ground. The system was upgraded in 2010 to add back-up grid power. There was no warning system in 1964.

With natural disasters becoming more frequent, Canadians are encouraged to be prepared.

“The recent earthquake and tsunami in Japan and the earlier earthquake in New Zealand show that an emergency can occur any time and any place- often without warning,” said Loretta Chandler, Director of Toronto's Office of Emergency Management in a media statement.

Chandler adds that it's important to know the risks and become 'emergency ready' with kits that include food, water and supplies to last at least 72 hours.

Coastal areas in BC are prone to minor earthquakes and in preparation for a possibly damaging event, the province takes part in a massive earthquake drill.

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