Researchers interested in the impact of an earthquake in the Vancouver area have released two new studies showing an earthquake that occurs to the southwest of the city could have a greater impact than previously thought.
The studies were published earlier this week in the periodical “Bulletin of the Seismological Society of America.”
“Historically, we know larger earthquakes could happen and so we are left at a crossroads,” said Sheri Molnar at the University of British Columbia Civil Engineering department and lead author of the studies.
“We know it can happen in the future, but we don’t have any tangible evidence of what that earthquake shaking [would be] like so the answer to that question was to run simulations.”
The researchers ran computer simulations that found sediments contained in the Georgia Basin, a geographical area of more than 18,000 km that includes Vancouver, would increase the ground motion of a potential quake by a factor of three or four times. The results mean that some larger buildings would likely experience greater shaking than originally thought.
“If the earthquakes occurred to the south or southwest of the basin, that would be the most hazardous to Vancouver because [seismic] waves have to travel northward towards Vancouver and have to travel over the southern portion of the basin, and that causes large surface waves to be produced,” said Molnar.
“Obviously, any earthquake directly below Vancouver would have the strongest impact.”
The B.C. provincial government is currently spending nearly a $1 billion to upgrade schools and retrofits bridges and condominiums, explains René Tinawi, manager at the Canadian Seismic Research Network (CSRN).
The network, comprised of seismic university researchers, was given funding over the last five years by the Natural Sciences and Engineering Research Council to research seismic conditions in Canada. CSRN’s research ended last year with final reports now being completed.
“The two major [earthquake zones] are Vancouver and the St. Lawrence Valley that includes Ottawa and Gatineau,” said Tinawi. “When I say St. Lawrence River, this includes the Montreal region as well as Quebec City … these are the two concerns.”
The Insurance Bureau of Canada released its own report in October of last year that examined the potential economic impact of an earthquake in both Vancouver and the Ottawa-Montreal region. In a scenario for Vancouver, it assumed an earthquake with a magnitude of 9 would occur 75 km away and then projected the costs to the economy.
“We wanted to know what the impact would be on the overall economy. The overall economic impact would run to $75 billion and insured would be $20 billion,” said Serge Corbeil, government relations manager for the West and Pacific at the Insurance Bureau.
“What we have found is that mitigation works. The author of the report concluded that all the new seismic structures would survive better than they thought.”
Another scenario for the Quebec City area showed that an earthquake of 7.1 magnitude with fault lines closer to the city would cause similar levels of instability and leave damages in excess of $60 billion.
“The damages there are also significant. A modelling for that region hadn’t been done before in terms of the economic impact. People in Quebec are not as aware of the earthquake risks as they should be,” said Corbeil.
Kaven Baker-Voakes is a freelance reporter based in Ottawa.
