Earthquake would shake east Ottawa hardest

Underground mapping conducted by area seismologists show most of Orleans in east Ottawa sits on Leda clay, which can increase the shaking felt during an earthquake.

Engineers can't always prepare for ground liquefying due to Leda clay

This 400-meter crater was caused by Leda clay in Notre Dame de la Salette, Que. after an earthquake shook Ottawa and West Quebec in 2010. Submitted photo

Recent studies show east Ottawa would feel an earthquake worse than much of the nation's capital.

Underground mapping conducted by area seismologists show most of Orleans sits on top of deposits of unstable Leda clay, which can magnify shaking felt during an earthquake.

Leda clay can also turn to liquid in certain conditions, which could cause the ground to crumble and flow away, while swallowing buildings.

"If the water table is very close to the surface and if you have soft soil during earthquakes, soil around the building liquefies," said seismologist John Adams from Natural Resources Canada.

"It loses its support and it doesn't matter how strongly the building was built. It will tip over."

Project underway to find Ottawa areas with most risk

Ottawa's micro-zonation project is trying to identify what parts of the city rest on Leda clay, which has become more urgent since the earthquake in Val-des-bois, Que., in June 2010.

An expert examines a land collapse that occurred in Notre Dame de la Salette, Que., one day after the Val-des-Bois quake that shook the Ottawa area. (Submitted photo)

One day after the earthquake hit the region, a 400-meter crater formed in Notre Dame de la Salette, Que.

The risk in Ottawa is now larger due to the Leda clay, which Adams said can amplify tremors by four to six times or even more during quakes.

Seismic engineers like Murat Saatcioglu work to mitigate risks from Leda clay, but he said sometimes liquefaction after earthquakes is impossible to prepare for.

The Ottawa and St. Lawrence valleys have seen numerous fatal slides of Leda clay, including one in Saint-Jude, Que., in May 2010. 

Ottawa is also at risk for a large earthquake that could be worse than February's deadly magnitude-6.3 tremor in Christchurch, New Zealand.

With files from the CBC's Evan Dyer