Damaging earthquakes are well known in the Pacific Northwest , including several larger than magnitude 7 , most notably the M9 1700 Cascadia earthquake and the M7 .0 – 7.3 earthquake in about 900AD on the Seattle Fault . The M6 .5 1965 Puget Sound earthquake shook the Seattle , Washington area , causing substantial damage and seven deaths . This event spurred the installation of the Pacific Northwest Seismic Network in 1969 to monitor regional earthquake activity
1700 Cascadia earthquake
1700 Cascadia earthquake
Pacific Northwest Seismic Network