In the offshore region to the west of Vancouver Island, more than 100 earthquakes of magnitude 5 or greater (large enough to cause damage had they been closer to land) have occurred during the past 70 years. Each year more than 1,000 earthquakes are recorded in western Canada. The Pacific coast forms the western border of British Columbia and is the most earthquake-prone region of Canada. However, the years between these events have been as few as 100 to 300 years - meaning, all Cascadia residents should prepare to experience a powerful and potentially damaging subduction zone earthquake in their lifetimes. The best available evidence indicates that these earthquakes occur, on average, every 500 to 600 years. Scientists believe the most recent subduction zone earthquake, a M9 event, occurred in January 1700. The Cascadia subduction zone lies offshore from northern California to southwestern British Columbia, where two tectonic plates - the North America plate and the Juan de Fuca plate - come together to form an 800-mile long earthquake fault. These far-away events, while not a part of Cascadia’s history, can teach us what to expect from future earthquakes in our region and can help us prepare and plan for them.Ĭascadia subduction zone – a regional threatĭifferent parts of Cascadia experience earthquakes differently (see below), in part because earthquakes arise from different sources. But the entire region shares the need to plan for a Cascadia subduction zone earthquake. Many recent earthquakes that grabbed headlines occurred outside of Cascadia, in countries such as Japan (Tohoku, 2011), New Zealand (Christchurch, 2011), Chile and Haiti (2010) and Indonesia (Sumatra, 2004). Earthquakes have struck offshore and inland, in small towns and busy city centers, in British Columbia, Northern California, Oregon and Washington. along the Seattle Fault, to the more recent Klamath Falls (1993) and Nisqually (2001) quakes, to the hundreds of small quakes that occur every year but go mostly unfelt throughout the region. Cascadia has a rich and diverse history of earthquake activity, from the magnitude 7.5 event thought to have occurred in 900 A.D.
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