Canada is a seismically active country that experiences thousands of earthquakes every year. An earthquake is the sudden movement of the Earth’s crust that releases energy in the form of seismic waves. While many of these events are small and go unnoticed, Canada has a long history of significant, potentially damaging seismic activity. The country’s vast geography spans multiple complex geological environments, creating different levels of earthquake risk across the nation.
The Tectonic Drivers Behind Canadian Earthquakes
The underlying causes of Canadian earthquakes differ significantly between the western and eastern parts of the country. Western Canada’s seismic activity is primarily driven by interplate seismicity, the interaction of tectonic plates at their boundaries. Along the coast of British Columbia, the Pacific Plate, the Juan de Fuca Plate, and the North American Plate are in motion. The Juan de Fuca Plate is actively sliding beneath the North American Plate in a process called subduction, forming the Cascadia Subduction Zone.
This boundary is currently “locked,” causing immense stress to build up over long periods. When this stress overcomes the friction, it will release as a massive megathrust earthquake, potentially reaching a magnitude of 8 or 9. Farther north, near Haida Gwaii, the Pacific Plate slides past the North American Plate, generating frequent, large earthquakes along a major fault system.
Eastern and Central Canada experience intraplate seismicity, occurring within the interior of the North American Plate, far from any active boundary. The causes are thought to be related to regional stress fields concentrated on pre-existing zones of weakness in the crust. These ancient, deeply buried faults can be reactivated by pressure exerted by the slow movement of the North American Plate away from the Mid-Atlantic Ridge.
Another factor in the east is post-glacial rebound, the slow upward movement of the crust after the last ice age melted the ice sheets. This ongoing adjustment creates additional stress that can trigger earthquakes along old fault lines. While generally smaller than West Coast events, their proximity to densely populated areas means they still pose a significant hazard.
Mapping Canada’s Major Seismic Hotspots
Seismic activity across Canada is concentrated in three main regions, each with a distinct geological source and level of hazard.
West Coast
The highest risk zone is the West Coast, encompassing the coastal areas of British Columbia and the Yukon. This area is subject to shallow crustal earthquakes and the threat of a massive Cascadia megathrust event off Vancouver Island, which last occurred in 1700. The Queen Charlotte-Fairweather fault system near Haida Gwaii is extremely active, frequently producing large earthquakes greater than magnitude 6. The risk here is heightened by the potential for tsunamis generated by large offshore ruptures.
Eastern Canada
A second major hotspot is located in Eastern Canada, primarily centered around the St. Lawrence and Ottawa River valleys. Specific high-activity areas include the Charlevoix-Kamouraska zone and the Western Quebec Seismic Zone. This region has experienced significant historical earthquakes, such as a magnitude 6 event in the Saguenay region of Quebec in 1988.
Canadian Arctic
The third area of concentrated activity is the Canadian Arctic, including the High Arctic and parts of Baffin Island. While often remote, this area experiences a high frequency of earthquakes, including some events that have reached magnitude 6 or greater. The seismic sources here are a form of intraplate activity.
Frequency and Strength of Canadian Seismic Activity
Canada experiences over 3,500 recorded earthquakes annually across the country and its offshore territories. The vast majority of these tremors are below magnitude 3 and are too small or too remote to be felt by humans. Only about 50 to 100 earthquakes are felt each year, with approximately three events of magnitude 5 or greater occurring every decade in Eastern Canada alone.
The size of an earthquake is measured using the Moment Magnitude Scale, a modern refinement of the older Richter scale. An increase of one whole number on the scale represents a release of approximately 32 times more energy. Earthquakes reaching a magnitude of 5 are considered the threshold for causing minor structural damage.
While large events are rare, they are a statistical certainty over long time scales. The largest recorded Canadian earthquake was a magnitude 8.1 event that occurred off the coast of the Queen Charlotte Islands in 1949. This demonstrates the capacity for the country to host major, destructive seismic events.
Seismic hazard mapping uses this frequency and strength data to inform the National Building Code of Canada. These maps calculate the probability of experiencing strong ground shaking, ensuring that building designs in high-risk areas can withstand anticipated levels of force. This quantitative approach helps engineers and planners mitigate the impact of future seismic events.