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Cascadia Subduction Zone
The Cascadia Subduction Zone is a long sloping fault that stretches from northern Vancouver Island to northern California, and is the most active seismic region in Canada.
This subduction zone is a type of convergent plate boundary, and separates the Juan de Fuca and North American plates.
'Great' subduction zone earthquakes are the largest types. Because earthquake size is proportional to the area of the fault, and because the fault area of the Cascadia Subduction Zone is very large, an earthquake of magnitude 9.0 or greater is possible.
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The last known 'great' earthquake occurred in January 1700.
 Click here for a map of earthquakes that have occurred in southwest British Columbia in the last 30 days .
Geological evidence indicates that great 'mega-thrust' earthquakes (magnitude > 8.0) may have occurred about seven times in the last 3,500 years, or about once every 500 years.
Large damaging crustal earthquakes (m > 6.0) occur more frequently, as recorded in 1918 (m = 7.0) and in 1946 (m = 7.3) on Vancouver Island, and in 1872 (m = 7.3) in Washington State.
Measurement of tectonic plate movements
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