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thumbnail of O-13-22 Open-File Report O-13-22, Cascadia Subduction Zone Earthquakes: a magnitude 9.0 earthquake scenario (2013 update), by Cascadia Region Earthquake Workgroup (CREW)

Also available as Washington Division of Geology and Earth Resources Information Circular 116 and British Columbia Geological Survey Information Circular 2013-3.

Download the full report PDF (4 MB)

Order publication CD, $15, from Nature of the Northwest. CD contains a 28-page PDF.

From the report:

IF YOU LIVE IN NORTHERN CALIFORNIA, WASHINGTON, OREGON, OR BRITISH COLUMBIA, YOU LIVE IN CASCADIA, a region remarkable for its stunning mountain ranges, rich farmlands and vineyards, beautiful beaches, great rivers, and green forests. It is a region of vibrant communities, busy international ports, and thriving businesses. Residents and visitors alike enjoy the cultural offerings of Cascadia’s cities and the diversity of outdoor activities at its natural areas. But the geologic forces that shaped the Northwest are still active: Cascadia is a region of earthquakes.

The Cascadia subduction zone is one of the principal sources of concern. Lying mostly offshore, this plate interface is a giant fault—approximately 700 miles long (1,130 km). Here, the set of tectonic plates to our west is sliding (subducting) beneath the North American Plate. The movement of these plates is neither constant nor smooth: the plates are stuck, and the stress will build up until the fault suddenly breaks. This last happened in 1700: the result was an earthquake on the order of magnitude 9.0, followed within minutes by a large tsunami—much like the earthquake and tsunami that struck Japan on March 11, 2011. Stresses have now been building along the Cascadia subduction zone for more than 300 years, and the communities of Cascadia can be certain that another great quake will again shake the region.

Because understanding the hazard is an essential step in preparing for it, the Cascadia Region Earthquake Workgroup (CREW) first published Cascadia Subduction Zone Earthquakes in 2005. Since then, scientists have further developed their understanding of the subduction zone, engineers have learned to build more resilient structures, emergency planners have made extensive use of earthquake and tsunami modeling tools to prepare more effectively, and the entire earthquake and emergency response community has learned volumes from recent subduction zone earthquakes and tsunamis in the Indian Ocean, Chile, and Japan. This second edition of Cascadia Subduction Zone Earthquakes incorporates these new developments and lessons, while also noting the progress that has been made since 2005 to prepare communities throughout the region for Cascadia’s next big subduction zone earthquake.

CREW is a non-profit coalition of business people, emergency managers, scientists, engineers, civic leaders, and government officials who are working together to reduce the effects of earthquakes in the Pacific Northwest.

Support for this publication was provided by FEMA, Department of Homeland Security, under the National Earthquake Hazard Reduction Program (NEHRP) State Cooperative Agreements. Points of view or opinions expressed in this document are those of the authors and do not necessarily represent the official position or policies of FEMA or the U.S. Department of Homeland Security.