Aftershocks off Haida Gwaii after major B.C. quake, but no major damage
The Canadian Press
Published Sunday, October 28, 2012 3:10PM PDT
Last Updated Sunday, October 28, 2012 6:21PM PDT
After a sleepless night of tsunami warnings and aftershocks, triggered by a massive earthquake off British Columbia's northwestern coast, Faye Beaulieu felt a small rumble inside her home around noon on Sunday in the Haida Gwaii community of Queen Charlotte.
It was yet another aftershock -- this time a magnitude-6.4, the most significant since the magnitude-7.7 quake the night before that itself was one of the biggest in Canadian history.
"I thought it was my washer going into spin cycle, but apparently it wasn't," said Beaulieu, 61, recalling the latest aftershock.
"It was only three or four seconds, just long enough to rattle everything --including me."
The main quake struck Saturday evening a few minutes after 8 p.m., with an epicentre about 30 kilometres off the coast of Haida Gwaii, formerly the Queen Charlotte Islands.
It triggered tsunami warnings along the B.C. coast and as far away as Hawaii. There were reports of people feeling the quake throughout B.C., though there appeared to be no injuries or significant damage in the immediate area beyond broken picture frames and dishes.
The largest wave associated with the quake hit Langara Island, a northern Haida Gwaii island, and measured just 69 centimetres.
Beaulieu, who is the unit chief for the community's ambulance service, was at home with her husband watching a movie and initially thought the rattling was from coming from her home entertainment system. But when she shut the movie off, the rattling didn't stop.
"I really thought my house was coming down," said Beaulieu, who said the shaking lasted about a minute.
"For how much the house was shaking, I'm surprised at how little happened."
Tsunami warnings prompted evacuations on Haida Gwaii and in other coastal communities such as Tofino, on the southwest coast of Vancouver Island.
Early Sunday morning, the warnings were downgraded to advisories, meaning evacuations were no longer necessary, and they were cancelled altogether a few hours later.
The area is a hot spot for quake activity, with a major fault line just off the coast of the islands that make up Haida Gwaii. It's the same area that saw Canada's largest earthquake ever recorded, a magnitude-8.1 quake in 1949.
Saturday's earthquake was Canada's largest since that 1949 quake, said John Cassidy, a seismologist with Natural Resources Canada.
"This was a huge earthquake -- a magnitude 7.7 is the type of earthquake that only happens maybe one or twice around the world each year," Cassidy said in an interview Sunday.
"It's Canada's equivalent to the San Andreas Fault."
The quake happened as two tectonic plates -- the Pacific plate and the North American Plate -- slid past each other. Cassidy said such horizontal movement typically doesn't pose the same tsunami risks as vertical movement, which is the sort of quake that triggered the devastating 2010 tsunami in Japan.
It was followed by "hundreds and hundreds" of aftershocks, most of them too small for anyone to feel. Cassidy said those aftershocks were expected to continue for days.
The quake invariably prompted speculation about the "big one" -- the type of earthquake that is believed to strike off the West Coast every 500 years or so and would create a massive tsunami and cause significant damage in British Columbia and the northwestern United States. The last one was in 1700.
Brent Ward, an earth scientist at Simon Fraser University, said the big one would happen along a different fault than the one involved in Saturday's quake, on the edge of the Juan de Fuca Plate west of Vancouver Island.
That plate is moving underneath the North American Plate, said Ward, in a process known as subduction. When it finally gives way, the results would be catastrophic.
"We would get the entire West Coast of Vancouver Island being affected by a large tsunami, similar in size to the one that hit Japan," he said.
"We would get intense ground shaking throughout southwestern B.C. down into Washington and possibly into Oregon, so we would see a very huge area affected by damaged buildings, damaged roads and bridges. There would be fatalities."
But Ward cautioned against focusing on the big one. He said smaller -- but still destructive -- quakes are likely to be more frequent, pointing to a magnitude-7.3 quake that struck underneath Vancouver Island, near the community of Courtenay, in 1946 as an example.
The damage in 1946 was considerable, and Ward said it would be worse today with the island more populated than before.
"Everyone's concerned about the big one, but the ones that are similar to what happened under Courtenay, these happen every 40 or 50 years," said Ward.
"If you compare similar sized earthquakes and the damage they do, it would be a very significant event."
In Haida Gwaii, 51-year-old Heather Barnes was spending Sunday cleaning up broken dishes. The night before, Barnes was about to cook dinner at her home in Skidegate, not far from Queen Charlotte, when the quake hit.
Barnes ordered her children to hide under a table. She managed to shut off the propane stove before taking cover herself.
"It was quite nightmarish," Barnes recalled.
"There was stuff crashing and breaking all around us. I was just terrified. I didn't know what we were going to see when it stopped."
The family's four cats ran around the house, and one of them was still skittish on Sunday, she said.
While the fears of a tsunami were never realized, there were concerns that information from the provincial government's emergency program was slow to reach local officials.
Justice Minister Shirley Bond, whose ministry oversees the province's emergency program, said the government will review what happened, but overall, she said she was pleased with the response.
"We're continuing to analyse the response as we work our way through the day. Local authorities responded well, and their emergency plans seem to have worked well," Bond said in an interview.
"Obviously, minutes and hours matter when there is a potential catastrophic event, so what I want to do is refine the process so that we do that as well as we possibly can."
Bond declined to offer her own assessment of the province's performance, preferring to leave it up to the government's review.