According to the Geographic Survey of Canada, a Canadian government department, the chance of a large subduction earthquake occuring in the NorthWest, is one in every 300 to 500 years. The last known one occured January 26, 1700, so we have a next event window of about 200 years. Earthquake prediction is not an exact science by any stretch of the imagination. Nobody really knows when the next big one will happen, all we know is that eventually, it will happen.