INDEPTH: FORCES OF NATURE Earthquakes in Canada: Surviving the moderate ones CBC News Online | Oct. 12, 2005
Canada is a veritable hotbed of seismic activity. The country averages three to four earthquakes a day more than 1,200 a year. The vast majority of them can only be detected by the sensitive equipment that measures seismic activity.
But a few times a year Canadians do feel the earth move. The most active parts of the country are the western and southwestern regions of British Columbia, including Vancouver Island and the Queen Charlotte Islands, which are struck more than 200 times a year. However, Eastern Canada has also been hit by major quakes, and experts cannot rule out a major earthquake hitting Toronto, Ottawa or Montreal.
Except for reports of one death in an earthquake in Montreal in 1732, nobody has ever been killed by a quake in Canada.
On Nov. 18, 1929, a magnitude 7.2 quake rattled the floor of the Atlantic Ocean about 250 kilometres south of Newfoundland, which was then a British colony. Nobody died from the quake, but 29 drowned after a tsunami swept across the Burin Peninsula.
June 23, 1946
August 22, 1949
Near Queen Charlotte Islands
July 10, 1958
June 24, 1970
South of Queen Charlotte Islands
December 20, 1976
West of Vancouver Island
February 28, 1979
December 17, 1980
West of Vancouver Island
December 23, 1985
Mackenzie region, NWT
November 12, 1988
Saguenay region, Quebec
The area immediately west of Vancouver is considered one of the most vulnerable in the country. In the Juan de Fuca Strait, two tectonic plates the North American Plate and the Juan de Fuca Plate rub against each other. The North American Plate is gradually sliding underneath its neighbour, building pressure along the plate boundary.
Eventually, scientists say, this will cause a "subduction earthquake," an incredibly powerful event that could measure up to a magnitude of 9. Based on geological evidence in the region, it's believed that such quakes strike every 300 to 500 years.
Eastern Canada is generally considered to be part of a stable continental region; many small fault lines straddle the Lake Ontario basin and the St. Lawrence River Valley, but the edges of the continental plates where most of the world's earthquakes occur are thousands of kilometres away.
"The crust is more rigid [in this region]," geologist Arsalan Mohajer of the University of Toronto told CBC News Online. "This is good news and also bad news. The good news is that we don't experience that many earthquakes. The bad news is that we don't know when the next possibly big earthquake will occur, because of a lack of information and data."
The last moderate earthquake in the region occurred on Sept. 25, 1998, when a magnitude 5.4 earthquake, centred just south of Lake Erie, rattled dishes and shook floors across Southern Ontario. A magnitude 5 quake shook the area 12 years earlier, in January 1986.
Getting up to code
Major Canadian cities in earthquake-risk zones:
Experienced two major earthquakes: 1918 (magnitude 7) and 1946 (magnitude 7.3).
Potential for a magnitude 9 quake from the Cascadia Subduction Zone, which lies offshore on the floor of the Pacific Ocean.
Densely populated city lies in the worst seismic hazard zone in Canada.
Damage to bridges during a major quake could isolate the city.
Intensive development in a region where the Earth's crust is being compressed. Moderate risk that stress could be released along nearby fault lines, causing considerable damage.
Earthquake in 1732 damaged 300 houses; another 185 were destroyed by fires following the quake.
City considered vulnerable due to large number of old buildings not up to modern building codes.
The Charlevoix Seismic Zone is fairly active, recording about 200 minor quakes per year. However, five quakes of at least magnitude 6 have been recorded in the past 350 years.
When urgent health, safety or other issues arise, the Canadian Commission on Building and Fire Codes (CCBFC) has the authority to make immediate changes to the National Building Code without holding public consultations.
Otherwise, changes to the code are made every few years. The most recent revision was released Sept. 23, 2005 the first major overhaul in 10 years.
The changes as they relate to safeguarding structures from the effects of earthquakes are described as "substantial." But you'd have to be an engineer to understand them.
They deal with issues such as period-dependent site factors, delineation of effects of overstrength and ductility, deflections and drift limits, and hazard in spectral format.
Cathy Taraschuk the National Research Council's senior technical advisor, structural design oversaw the latest revision to the National Building Code. It's a process of looking at the latest research on how buildings behave in earthquakes and determining how to take that information and make Canadian buildings safer.
The code's recommendations vary depending on what part of the country you may be building in. A building in B.C., for instance, should be built to withstand a stronger earthquake than one built in Manitoba.
"It varies depending on where you live in the country," Taraschuk told CBC News Online. "It's the same as for snow or wind some areas have to withstand more of a load."
"We've moved more to site-specific recommendations this time."
In other words, it not only matters which part of the country the building is erected in, it also matters where in the city it's built. The shaking from a magnitude 6 quake, for instance, would be more pronounced in an area where the soil was soft or sandy.
Another major change in the code, according to Carlos Ventura, is that the new provisions require buildings to be able to withstand a much stronger quake.
Securing a water tank to the walls and the floor reduces the risk that it will be tossed across a room during an earthquake. Photo courtesy of The Institute for Catastrophic Loss Reduction.
"Under the old code, buildings had to be able to withstand an earthquake that might happen in a region once every 575 years," Ventura, the director of the earthquake engineering research facility at the University of British Columbia, told CBC News Online. "Under the new code, it's an earthquake that might occur once every 2,000 years."
If you've bought a house in this country over the last few hundred years, you've bought a structure that is not covered by either the National Building Code or the building code of your province or territory.
That was one of Ventura's major problems with the old code and he's concerned it hasn't been changed under the new code. Ventura has conducted extensive research into how houses fare when the ground beneath them moves.
His findings suggest that most houses in the country would remain standing after an earthquake. But many would be uninhabitable.
"The lessons learned were about the type of damage suffered," Ventura said. "People would not be able to live in those houses because of the damage suffered. They would have to fix them and that would mean hundreds of families would be homeless maybe for months. The socio-economic impact would be unacceptable."
Paul Kovacs the executive director of the Institute for Catastrophic Loss Reduction agrees that the changes to the code should have gone a lot further when it comes to houses.
"Earthquakes and storms continue to do a lot of damage to buildings," Kovacs said. "The building code is very good in Canada and the changes help. But theres more we can do to make our buildings safer."
Anchoring heavy furniture to the wall will keep it from tipping over in an earthquake. Photo courtesy of The Institute for Catastrophic Loss Reduction.
The institute recently started a safer building program, through which it comes up with ways to make buildings better able to survive severe storms and earthquakes.
As part of the program, the institute retrofitted a house in Vancouver in May 2005 to make it better able to withstand an earthquake. Kovacs estimates that for about $1,000 you can minimize the risk of being injured in your home during a quake. He says earthquake-proofing new homes would add about one-half to one per cent to the total cost of the house.
So far, insurance companies have expressed interest in getting involved. Kovacs says the next step is to get homebuilders to buy in.
When the code was updated this time around, the committee in charge of the section of code dealing with houses and small buildings had proposed standards on earthquake resistance. But several provincial officials expressed their concerns at a meeting in April 2004.
In the end, the Canadian Commission on Building and Fire Codes decided once again to exempt houses and small buildings from earthquake safety requirements. Instead, it recommended that further study of the issue should be a priority for the next code development cycle.
Go through your home, imagining what could happen to each part of it if shaken by a violent earthquake.
Teach everybody in the family how to turn off water, electricity and natural gas. (Don't shut off the gas unless there is a leak or a fire. If the gas is turned off, don't turn it on again. That must be done by a qualified technician.)
Make sure the house is bolted to its foundation.
Make sure the walls are braced.
Make sure the chimneys are strong and well-braced.
Tie down the water heater and other heavy appliances (stove, washer, dryer) that could break gas or water lines if they topple.
Secure top-heavy furniture and shelving units to prevent tipping. Keep heavy items on lower shelves.
Affix mirrors, paintings and other hanging objects securely so they won't fall off hooks.
Locate beds and chairs away from chimneys and windows. Don't hang heavy pictures and other items over beds.
Use safety latches on cupboards to stop contents from spilling out.
Keep flammable items and household chemicals away from heat and where they are less likely to spill.