Earthquakes
Seattle, Tacoma, Washington Earthquake Awareness Through Oct. 17: M9 Cascadia Risk
SEATTLE, Wash. — A massive earthquake capable of reaching magnitude 9 remains one of Washington's most serious natural hazards, with Seattle, Tacoma and surrounding Puget Sound communities facing the
By Mason Reid · 2026-10-13T12:53:13.970Z
SEATTLE, Wash. — A massive earthquake capable of reaching magnitude 9 remains one of Washington's most serious natural hazards, with Seattle, Tacoma and surrounding Puget Sound communities facing the possibility of devastating shaking from multiple active fault systems.
The threat is drawing renewed attention as earthquake awareness efforts continue through Saturday, Oct. 17, with more than 1.4 million Washington residents already registered for Thursday's Great Washington ShakeOut.
According to the Washington Department of Natural Resources, the Cascadia Subduction Zone stretches more than 500 miles offshore, from northern California to Vancouver Island.
The enormous fault system last produced an estimated magnitude 9 earthquake on Jan. 26, 1700, generating a tsunami that traveled across the Pacific Ocean to Japan.
Scientists warn that another major earthquake along Cascadia is inevitable, although they cannot predict when it will occur.
The U.S. Geological Survey's latest regional estimates indicate a 15% probability of a magnitude 9 Cascadia megathrust earthquake over the next 50 years.
But Cascadia is not Washington's only earthquake threat.
The Seattle Fault, which runs beneath the metropolitan area, is capable of generating an earthquake estimated between magnitudes 6 and 7.5. Other active faults extend through the greater Puget Sound region, creating additional hazards for Tacoma, Olympia and neighboring communities.
Earthquake related soil liquefaction is another concern, particularly in low lying waterfront areas constructed on artificial fill or water saturated sediment. During severe shaking, those soils can lose strength, damaging roads, foundations and underground utilities.
Washington's earthquake history includes the magnitude 6.8 Nisqually earthquake in February 2001, which damaged buildings and infrastructure across the Puget Sound region.
The potential for another damaging earthquake is driving participation in the Great Washington ShakeOut on Thursday, Oct. 15, at 10:15 a.m. Pacific time.
The Washington Emergency Management Division announced that approximately 1.4 million people had registered as of Oct. 6.
Students, businesses and households will practice dropping to their hands and knees, taking cover beneath sturdy furniture and holding on until shaking stops.
The exercise will also include testing more than 120 tsunami warning sirens along Washington's inner and outer coastlines.
Unlike routine monthly tests, the sirens will produce their actual tsunami warning sounds. Officials emphasize that the activation is only a drill and residents should not call 911 because of the test.
Radio and television emergency alert systems will also be tested, while the Wireless Emergency Alert system used for cellphone warnings will not be activated.
For communities along Washington's Pacific coastline, a major Cascadia earthquake presents the additional danger of a destructive tsunami. Residents in designated tsunami hazard zones should know evacuation routes leading to higher ground.
Emergency officials encourage families to secure heavy furniture, store food and water, establish communication plans and prepare for potentially prolonged interruptions to essential services.
Although no earthquake can currently be predicted with enough precision to provide a reliable date or time, Washington's extensive fault systems make preparedness a continuing priority.
For Seattle, Tacoma and communities throughout western Washington, this week's earthquake awareness activities offer an opportunity to prepare before the next major seismic event.