Earthquakes in British Columbia

Off the coast of southwestern British Columbia is a convergence of two tectonic plates, which causes most of the earthquakes felt in the area.

The following exerpt was taken from the Geological Survey of Canada, which also provides:

• Earthquake zones of Western Canada.

Where Earthquakes Happen

Each year, seismologists with the Geological Survey of Canada record and locate more than 1000 earthquakes in western Canada. The Pacific Coast is the most earthquake-prone region of Canada. In the offshore region to the west of Vancouver Island, more than 100 earthquakes of magnitude 5 or greater (large enough to cause damage had they been closer to land) have occurred during the past 70 years. Part of the Pacific Ring of Fire, the concentration of earthquakes along the west coast is related to the presence of active faults, or breaks in the earth's crust. The surface of the earth is always changing, as the earth's crust is made up of "plates" (like pieces of a jigsaw puzzle) that are constantly moving relative to one another at speed's of about 2-10 cm/year (about how fast your fingernails grow). The plates can either slide past one another or they can collide, or they can diverge (move apart).

The west coast of Canada (click here for cartoon) is one of the few areas in the world where all three of these types of plate movements take place, resulting in significant earthquake activity. Earthquakes in this region occur along the faults in the offshore region (e.g., the M=8.1 Queen Charlotte Island earthquake of 1949); within the subducting ocean plate (e.g., a magnitude 6.5 earthquake beneath downtown Seattle in 1965); and within the continental crust (e.g., a magnitude 7.3 earthquake on central Vancouver Island in 1946). Moving inland from the coast (and the active plate boundaries), the frequency and size of the earthquakes decreases. Saskatchewan and Manitoba are the least earthquake-prone areas in Canada.

Past Earthquake History

The Geological Survey of Canada provides:

• Map of recent earthquakes in Canada.
• Seismicity Map of Canada.
• Largest Historic Earthquakes of Western Canada.

Earthquake Hazard Information You Should Know

• Earthquake Hazards in Canada - from the GSC
• Seismic Hazard Maps of Canada - from the GSC
• Seismic Hazard Maps of Victoria
• Expected Ground Motion from Future Earthquakes
• Earthquake Hazard Map for British Columbia used in the Uniform Building Code
• Mitigation strategies for your business
• Mitigation strategies for your home