The lithosphere, Earth's brittle outer skin, is divided into large 'plates' that continuously move towards, away from, or past each other. Stresses occur in the Earth where plates push together or past each other. Occasionally, rocks rupture along a fault, causing energy to be released as an earthquake.

Great subduction zone earthquakes release 30 to 100 times more energy than the 1946 earthquake, but fortunately occur only once every 500–600 years, on average. The most recent of the great earthquakes, in January 1700, triggered a tsunami that destroyed First Nation villages on the west coast of Vancouver Island.

Want more information on earthquakes?  Visit the Earthquakes Canada Web site.