Cascadia subduction zone (Wikipedia) The Cascadia subduction zone is a 960 km (600 mi) fault at a convergent plate boundary, about 112-160 km (70-100 mi) off the Pacific Shore, that stretches from northern Vancouver Island in Canada to Northern California in the United States. It is capable of producing 9.0+ magnitude earthquakes and tsunamis that could reach 30m (100 ft). The Oregon Department of Emergency Management estimates shaking would last 5-7 minutes along the coast, with strength and intensity decreasing further from the epicenter. It is a very long, sloping subduction zone where the Explorer, Juan de Fuca, and Gorda plates move to the east and slide below the much larger mostly continental North American Plate. The zone varies in width and lies offshore beginning near Cape Mendocino, Northern California, passing through Oregon and Washington, and terminating at about Vancouver Island in British Columbia.