Recent nearby earthquakes no reason to panic


photo courtesy of natural resources canada


A Port Alberni bank is seen in this 1946 photograph after a magnitude 7.3 earthquake hit Vancouver Island.



The three earthquakes that hit the Pacific Northwest in the past week needn’t have people in earthquake-prone Vancouver packing up and heading east just yet.

John Cassidy, a seismologist with the Geological Survey of Canada, said while it’s unusual to have so many higher-magnitude earthquakes in such a short time, they’re not a sign the Big One’s imminent.

Magnitude-5.6 and 6.5 earthquakes hit the Queen Charlotte Islands and Bella Bella on Jan. 5, while a magnitude-6.4 earthquake was recorded off the Oregon coast on Wednesday.

"This is the most seismically active area in Canada, and we’ve seen much larger earthquakes in the past," said Cassidy.

In 2001 an earthquake hit Seattle and caused about $2 billion in damage. It was felt in Vancouver.

Cassidy said there are up to 400 tiny earthquakes in Vancouver every year.

This map shows where the 10 biggest earthquakes have hit Canada in the last 350 years. The largest was a magnitude-9 quake that hit B.C. in 1700.

"Earthquakes that are large enough to cause damage occur, on average, decades apart," he said, adding that British Columbia’s last big earthquake hit Victoria in 1946.

"The really giant earthquakes — the magnitude nines that happen centuries apart — the last one was in 1700. Those earthquakes are about 500 years apart."

"From Northern California to Northern Vancouver Island there is a region where a new ocean plate is being created offshore. That plate is colliding with North America just off Vancouver Island and sinking below Victoria and Vancouver, and it causes earthquakes."

"We can’t predict them," he said. "What we’re working on is better understanding where energy is being stored in the rocks for future earthquakes to get a better idea of where earthquakes are more likely (to hit), how large they can be and roughly how often they occur."

quake ready?

  • New buildings in Vancouver must conform to seismic requirements set by the city and modelled after the Provincial Building Code.

  • There is no by-law requiring older buildings to upgrade except when managers seek building permits for renovation.

  • A 1995 study funded by the city suggested around 8,000 older Vancouver buildings don’t meet current codes and could be vulnerable in an earthquake.