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Past and Future Earthquakes in Eastern Canada

The study of past earthquakes in eastern Canada helps reduce the consequences of future seismic events. Most significant events of the past have occurred inside source zones that are also active with lower magnitude activity. We know that the earthquakes of 1663 (Magnitude 7), 1791 (M 6), 1860 (M 6), 1870 (M 6½) and 1925 (M 6.2) all occurred in the Charlevoix-Kamouraska Seismic Zone. The damaging earthquakes of 1732 in Montréal (M 5.8), 1935 in Temiscaming (M6.2), and 1944 under Cornwall-Massena (M 5.6) occurred in the Western Québec Seismic Zone.

In June 2010, a magnitude 5.0 earthquake occurred 50 km North of Ottawa in the latter seismic zone. On the other hand, the 1988 Saguenay earthquake was well outside the Charlevoix Zone, in a typical Canadian Shield environment with little background activity. These earthquakes are all included into the seismic hazard estimates. In the most recent seismic zoning exercise, the inclusion of a geologic model has raised the seismic hazard levels in areas of the St-Lawrence paleorift region and in the Saguenay and Ottawa-Bonnechere grabens. For moderate to large earthquakes, the seismic resistance standards of the National Building Code of Canada should provide a good level of protection to newer buildings. Older buildings that were not designed with such protection represent a source of danger.