1700: Cascadia Subduction Zone earthquake and tsunami, magnitude 9.0 or above. Through Native American stories and geological evidence such as land levels, tree rings, tsunami traces and historic records, seismologists have pieced together data on this, the most devastating quake on record in the Pacific Northwest. This quake rocked the region with strong shaking for many minutes. Subduction earthquakes occur rarely, about 300 to 500 years, but they can be deadly.
1872: Crustal Earthquake near Entiat in the North Cascades, magnitude 7.4. This is the largest historical shallow crustal earthquake on record. The 10 mile shallow quake was followed by many aftershocks.
1949: Deep Earthquake near Olympia, magnitude 7.1.
2001: Nisqually earthquake, magnitude 6.8. This is the quake Puget Sound residents won’t forget. It was one of three recent deep quakes; the others were in 1949 and 1965. All occurred roughly 40-miles deep in the oceanic plate beneath the continent. The 1965 deep earthquake between Seattle and Tacoma was a magnitude 6.5.
Note: An earthquake over magnitude 6.0 is considered severe. Information was supplied by the Pacific Northwest Seismic Network.