Earthquakes in Seattle

Seattle sits in a high seismic-risk zone, exposed to three distinct earthquake sources. Offshore lies the Cascadia Subduction Zone, where the Juan de Fuca plate slides beneath North America and periodically ruptures in magnitude-9 megathrust events — the feared "Big One" of the Pacific Northwest, last recorded in January 1700. Beneath the metropolitan area, the shallow Seattle Fault can produce damaging quakes close to the surface, and deep intraslab earthquakes add a third threat that the region experiences roughly every few decades.

The most recent significant shock was the magnitude-6.8 Nisqually earthquake of February 2001, a deep intraslab event that injured hundreds and caused billions in damage across the Puget Sound region. Geologists studying the Seattle Fault have found evidence of a large surface-rupturing quake around AD 900 that lifted shorelines and triggered a tsunami in Puget Sound. With soft, water-saturated soils in low-lying neighborhoods prone to liquefaction, Seattle remains one of the most seismically vulnerable major cities in the United States.