Although two recent earthquakes have raised fears over additional tremors in B.C., a Canadian seismologist says neither raised the risk of the “Big One.”
Honn Kao, an earthquake seismologist with Natural Resources Canada, said the timing of Wednesday’s 5.8 magnitude quake near Haida Gwaii and Saturday’s 7.1 magnitude quake in southern California was purely coincidental, as each instance was occurring along entirely different “tectonic settings.”
British Columbians have long been warned to prepare for the “Big One,” a megathrust earthquake expected to hit somewhere along the Cascadia subduction zone, which runs along the west coast from northern Vancouver Island to northern California. A megathrust earthquake can occur when one tectonic plate slips under another.
“There is not a scientific basis to use the Haida Gwaii earthquake as any kind of prediction tool for any occurrence of the Big One,” Kao said, and the one in the U.S. was too far from the Cascadia zone.
More than 100 earthquakes (including M6.3, M5.8, and M5.1 events) along the coast of #BritishColumbia during the past month.
Anytime is a great time to register for @ShakeOutBC https://t.co/ALddNkID6R
and to update your emergency kit @PreparedBC https://t.co/4AFCKuKZAW#NRCanSci pic.twitter.com/HDDFYcs0wj
— John Cassidy (@earthquakeguy) July 9, 2019
But Kao said people living in B.C.’s coastal regions should still be watchful.
“On average, the megathrust earthquakes happen every 500 years,” he said. “We found that the shortest time interval between megathrust earthquakes is 250 years, while the longest interval was 800 years.”
The last megathrust earthquake happened in 319 years ago in 1700.
“We are definitely into the next cycle… so people should be well prepared for the strike of the next earthquake.”
In terms of what residents should expect, Kao pointed to the 2004 Indian Ocean Boxing Day earthquake and tsunami and the 2011 earthquake and tsunami that hit Japan.
The Indian Ocean quake came in at a magnitude of 9.1 and killed 227,898 people, while the quake in Japan hit just off the country’s eastern coast on March 11, 2011, and killed nearly 16,000.
Kao said a megathrust quake off the B.C. coast could have similar consequences, and since scientists aren’t yet able to predict such quakes before they happen, people should get prepared now.
When the “Big One” does hit, early warning systems will give people living nearby between five seconds and one minute of advance notice.
To learn about how to prepare for an earthquake or tsunami, read the provincial government’s guide.