Seattle Field Office, Seattle, WA

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. Activities include collaboration with the University of Washington in contributing to the Advanced National Seismic System through operation of the Pacific Northwest Seismic Network.

  •  Preparedness

    In Cascadia strain arises from the interaction of three tectonic plates. The North America, Juan de Fuca, and (idirectly) the Pacific Plate all are moving with different trajectories.

  •  Additional Information About Pacific Northwest Earthquake Science

    The Pacific Northwest Seismic Network (PNSN) in Seattle is home to USGS and University of Washington scientist who monitor and study earthquakes in the Pacific Northwest.

  •  Seattle Hazard Maps

    A high resolution view of the potential for strong earthquake shaking in the Seattle area