The spectacular scenery of the Pacific Northwest results directly from the active geological processes associated with being part of a subduction zone. The Pacific Northwest includes Washington, Oregon, northern California, and southwestern British Columbia, and geologically shares many similarities with the subduction zones of Japan and Chile. Instrumental, written, and geological records from the region tell of earthquakes from three generalized sources. Earthquakes as large as magnitude 7 originate in the subducted Juan de Fuca plate, mainly beneath the Puget Sound region. Moderate and large earthquakes occur also on faults within the overriding North America plate, on both sides of the Cascades. Great earthquakes, as large as magnitude 9, happen on the boundary between these plates. Earthquakes from any of these sources may set off landslides, liquefaction, and tsunamis.

USGS earthquake studies of this region are intended to help reduce the losses earthquakes may cause.

University of Washington campus with Mt. Ranier in the background. (Courtesy of Joe Becker.)

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