A tsunami from 9.0 earthquake would reach B.C. coast in about 20 minutes, research finds

If a magnitude 9.0 earthquake struck in the Cascadia subduction zone, along the B.C. and U.S. coast, tsunami waves would reach the outer coast of northwest Vancouver Island in about 20 minutes.

The waves would be an estimated 5.9 metres high, followed by runup on the land that may exceed 12 metres of elevation.

This is just part of the findings of a coastal hazard assessment plan for B.C.’s coast in order to help communities and the province plan for emergencies.

Research from Ocean Network Canada (ONC), Strathcona Regional District and Northwest Hydraulic Consultants, as well as Ka:’yu:’k’t’h’/Che:k:tles7et’h’ First Nations and Nuchatlaht First Nation, will help determine the estimated arrival times and flooding extent of earthquake-induced tsunamis on the B.C. coast.

“The objective of our project was to first identify the hazard in the study area, what is the tsunami wave height, current velocities and time of arrival of tsunamis, and also how to communicate those hazards with the public through several hazard and foundation maps that we created for the project,” Soroush Kouhi, an applied scientist specialist at Ocean Network Canada told Global News.

“It’s important to raise the awareness of the public through the information that we have provided in this project.”

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Kouhi said one of the biggest takeaways from the project is how quickly the tsunami waves could arrive on parts of B.C.’s coast in less than 30 minutes if the quake strikes in the Cascadia subduction zone.

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He added the communities on the west coast of Vancouver Island and others such as Tahsis and Zeballos are at the greatest risk of a dangerous tsunami.

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“We regularly work with communities on their tsunami activities preparedness and plans,” Minister of Emergency Management and Climate Readiness Bowinn Ma told Global News Tuesday.

“We have funding provided through the Community Preparedness Fund to support communities in work that they do so as an example, Tofino recently received funding to plan a vertical escape structure for their residents.”

Ma said the province does have staff 24 hours a day, 365 days a year, monitoring seismic activity off the coast and if a tsunami could occur at that time. She added that if a risk of a tsunami is determined, then the provincial government does have the ability to broadcast emergency alerts to communities at risk.

“I was out in Ucluelet just in April and participating in their high-ground hike,” Ma added. “So communities, during tsunami preparedness week, perform or often engage in these high-ground hikes and tsunami preparedness activities where they practice with the community where the high ground is in a community.”

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Kouhi said the results of this project can help communities better prepare for tsunamis and update their emergency plans.

Archie Little, a councillor with the Nuchatlaht First Nation, located just west of Zeballos, said he remembers the 1964 tsunami that struck Port Alberni.

That tsunami was caused by a magnitude 9.2 earthquake off the coast of Alaska.

“The tsunami produced by the earthquake swept southward along the British Columbia coast, and into the coastal passages and fiords. It penetrated up rivers, and was even recorded at Pitt Lake, a fresh water tidal lake over 30 miles from the sea,” according to a report from Fisheries and Oceans Canada.

Little said he was in residential school on Meares Island, at the time, and the tidal waves hit in the afternoon.

“The tide came in about two or three times and came up a couple of hundred feet, just came in and out,” he added.

ONC also helped produce a documentary on the history of tsunamis on the West Coast from an Indigenous perspective.

Little said they showed the documentary in Port Alberni but many young people didn’t attend.

“Those are who we need to focus on to ensure that they know, to ensure that they are ready and not to wait until the last minute to start grabbing stuff because it will be too late.

“It’s coming. It’s just a matter of when and the more we’re prepared, we’ll survive.”