2010 quake led Ottawa to change policies

A magnitude 5.0 earthquake that struck western Quebec and rattled the national capital region in 2010 led the city of Ottawa to change its policies on how people should respond should another quake strike.

The Val-Des-Bois quake, centred about 60 km north of Ottawa, shattered windows and shook buildings, knocking down a brick chimney in at least one building. Outside the city, the damage was more extensive, damaging a church in Gracefield, Que., and collapsing a section of Highway 307 near Bowman, Que.

But the lasting impression for many in Ottawa's downtown was how office buildings across the city evacuated, with workers pouring onto the street.

Seismologists and disaster management experts say that was the wrong move, since it exposed them to potential dangers from falling glass or other debris.

With most buildings in Ottawa built to withstand this type of earthquake, workers instead should have taken shelter inside.

"Our biggest lesson learned was the need to make sure we communicate with the business community to ensure they have policies and procedures around what to tell employees when earthquake happens," said John Ash, the city's chief of security and emergency management.

Nash said the city needed to look at how to prioritize responses based on severity. For example, he said during the quake the fire alarm system went off at city hall. While the natural response of staff was to exit the building, he said the correct response would have been to wait inside for the alarm to stop or for instructions.

ByWard market buildings vulnerable

The city has since altered its information for building managers, and now says only people in older, unreinforced masonry buildings like those found in the ByWard market should exit their buildings should another quake strike. Everyone else should remain indoors, he said.

That follows the research of Kate Ploeger, a PhD student at the University of Ottawa who is working with the University of Ottawa's hazard mitigation and disaster management research centre to assess Ottawa's earthquake readiness. A study should be completed in two years.

Ploeger said Ottawa is behind only Vancouver and Montreal among Canadian cities when it comes to earthquake risk. The lack of earthquake preparedness of Ottawa residents factored into that assessment. For instance, while many people evacuated buildings and went to the street last year, they may have been wiser to seek shelter under a solid desk.

Ploeger defines risk as a combination of the potential hazard — based on both the potential for ground motion under a building and the building materials — and vulnerability — based in part on the number of people in a building.

She said an earlier risk assessment she conducted of close to 600 buildings in the city's core found a number of potential trouble spots should a more serious quake occur — such as a magnitude 6.0 quake close to the city.

Ploeger said the high number of rigid, unreinforced masonry buildings in the ByWard Market made that area a likely spot for the most structural damage, but said debris was most likely to occur in the south side of the city's downtown, where more high-rise buildings are in place.

Parliament Hill on solid bedrock

"But the area with most casualties was around Parliament Hill and this whole downtown block, because there are a lot of people," said Ploeger. "The census tracker says this is an area with 65,000 people coming into work."

Parliament Hill itself is not a likely site for damage, she says, because it sits on solid bedrock, meaning the ground does little to amplify a tremor.

By comparison, she said, the newly refurbished Museum of Nature was reinforced against earthquakes because it sits on offshore marine sediment with a substantial amount of clay, and is therefore more prone to shaking when a quake occurs.

Ottawa is near a relatively active fault line that runs parallel to the St. Lawrence Valley. The most recent comparable earthquake on that fault line was a 5.4-magnitude temblor in 1998.