The earthquake that was felt Friday by many Island residents should serve as a wakeup call, says a geoscience expert with Simon Fraser University.
The quake, now classified as a 6.4 magnitude event, was centred off the coast of Vancouver Island, just over 80 kilometres miles offshore from Port Alice.
Simon Fraser University geologist Brent Ward said while the event didn’t appear to cause any significant damage, it stands as an example of what can happen to communities situated on the so-called ring of fire on the Pacific Rim — and he warned it’s time the people who live there to take the threat seriously.
“This is a great wake up call,” he said in an interview Friday. “It’s something that should make everyone realize we live in a tectonically active area. “
To this end, he said, people should make sure they have an earthquake kit, containing everything they would need to survive on their own for at least 72 hours.
“You’re going to be on your own for several days after a large quake,” he said. “You’ll need water, food, flashlights and warm clothes.”
Friday’s quake was originally classified as a 6.7-magnitude event and three tremblors, a 6.7, a 6.4 and a 6.6 were reported in the same area at the same time, preceded by a much smaller, magnitude 2.1 quake about four hours earlier, also in the same area.
However, Ward said this could be the result of initial confusion as the data rolled in from different parts of the globe.
“When I first looked at the U.S. Geological Survey site it had it as 80 kilometres deep and a magnitude of 6.7, and now it has changed to 6.4 and shallower. When it first happens, it is picked up by a bunch of seismometers and the initial calculation of its size and where it is, gets better as more and more stations report. In the first few minutes or hour or so, it kind of moves around a bit.”
Ward said there’s currently no way to tell if the shaker was a precursor to something larger, noting that, with the scientific knowledge available to date, this can only be determined in hindsight.
“You don’t really know it’s a precursor until you get a bigger one later,” he said. “That’s the problem. Because so much work was done on the Japanese quake, they noticed there were a couple of small earthquakes that were precursors, but we get little ones all the time, so whether it’s a precursor or just a small earthquake remains to be seen.”
The quake, he said, was a relatively minor event, noting the largest one measured in the area — the 1946 earthquake centred under Buttle Lake, had a magnitude of 7.4.
“It caused extensive damage in Courtenay and Comox,” he said. “There were a lot of chimneys that broke off and fell into or beside the houses. A lot of brick buildings were damaged and there were numerous landslides and liquifaction as well.”
Liquifaction occurs when loose, sandy soil takes on the properties of a liquid during prolonged shaking, causing buildings and other structures to tilt or sink.
He noted as well that scientific evidence gathered about an earthquake on Vancouver Island 1700 indicates it was a whopping 9.0 event.
It may have been relatively small, but the quake was disturbing enough to many people who felt the ground move at
The tremblor, struck at 12:40 p.m. and lasted for 15 to 20 seconds, was felt strongly by Bowser resident Gail Carr.
“I was sitting at my computer and the whole house shook — the floor, the roof, everything,” she said. “even the hanging plant was moving in the kitchen.”
Carr ran outside and remained there as she waited to see if more quakes would come.
Qualicum Woods resident Myrett Drummond also felt the shaking.
“The desk and chair were going in a small circle,” she said. “I’ve got a fan with hanging controls and they were swinging a bit, too, but not wildly.”
Ward said the shaking was caused by a crustal quake.
“That is a quake that occurs in the North American crust,” he said. “That’s because the Juan de Fuca and Explorer plates are being pushed underneath the edge of North America and the contact between those plates is kind of stuck, so pressure starts to build up. It’s not sliding freely, so every so often you get a rupture in the rock.”