New B.C. highrises at risk in event of major quake
Published Wednesday, January 26, 2011 8:58PM PST
New apartment and office buildings on Canada's west coast may be in serious danger of toppling and crumbling during "the big one," according to an engineer who says he has uncovered a serious flaw in the way modern buildings are constructed in B.C.'s earthquake zones.
The news comes on the 311th anniversary of one of the strongest earthquakes ever recorded on North America's Pacific Coast. Known as a "megaquake," it would have shook the ground for at least five minutes.
Perry Adebar of the University of B.C. Earthquake Lab surveyed the damage of the 8.8-magnitude Chilean megaquake in 2009 that killed hundreds of people. He wanted to find out why many of the severely damaged buildings were new while most of the older buildings withstood damage.
His findings reveal a major flaw in new building techniques. Many newer buildings in Chile use six-inch concrete walls for support but Adebar discovered those walls are not as earthquake resistant as previously thought.
The thinner walls have become popular in both Chile and North America because they allow for additional parking in underground parkades -- where buildings need to be their strongest.
Construction rules, known as building codes, in Chile and Canada are nearly identical. Adebar believes many buildings with identical flaws exist in British Columbia, putting dozens of structures at risk during a megaquake.
He simulated the earthquakes in his lab to test the performance of thin walls.
The findings have prompted him to call for urgent changes to the way buildings are constructed in B.C.
Adebar says buildings between 10 and 20 storeys are at the highest risk during a megaquake. He says buildings built on flood plains and on sandy soils, similar to Richmond, south of Vancouver, had the biggest problems in Chile.
"Chile is a very modern country and we have six-inch walls just like this in Canada," he said.
Mark Miller of the Discovery Channel-Daily Planet says the findings mean building codes up and down the West Coast will have to be changed.
Adebar says buildings can be reinforced by wrapping thin walls with carbon fibre but it's a fix that could take years and cost millions of dollars.
The subduction zone near B.C. is longer than the one in Chile, which means when a big earthquake hits Vancouver, the ground could shake for twice as long –- up to four minutes.
Chile's earthquake was what's referred to as a subduction quake. They are 100 times more powerful than the great San Francisco earthquake of 1906.