It can be several minutes. This long duration can result in damage to some types of buildings that might not be damaged at the same strength of shaking produced by a smaller earthquake. The Kobe earthquake was right beneath the city and the megathrust earthquake will be about 150 kilometres from Vancouver. The damage pattern would be very different. Vancouver can expect to experience if we look at what happened to Anchorage, Alaska, during the 1964 magnitude 9.2 megathrust earthquake.
Anchorage is about the same distance from the Alaska subduction fault.
Small buildings generally had little or no damage, unless they were affected by landsliding. Almost all the damage involved large buildings or large structures such as bridges. Inland earthquakes, which are not as big but can be much closer to our urban areas and occur much more frequently, are our biggest earthquake hazard. The thrusting motion of megathrust earthquake causes large vertical movement on the sea floor and this displaces a large volume of water which travels away from the undersea motion as a tsunami. Vancouver Island is part of the North American plate.