Seattle Seismic Zone • 250 km Monitoring Radius
Real-Time Earthquakes in Seattle, United States
Live seismic telemetry, active fault rupture tracking, and ground motion hazard monitoring for the Seattle metropolitan area.
Landmark Historical Earthquakes in Seattle
Significant seismic benchmarks, cataloged damage, and engineering lessons shaping modern safety standards.
Three Lakes / Monroe, Snohomish County
Jolted the Seattle metropolitan area awake in the early morning; strongly rattled downtown high-rises and residential neighborhoods from Everett to Tacoma, triggering precautionary structural inspections across Washington State bridges.
Nisqually / Anderson Island
Deep intra-slab Wadati-Benioff earthquake 52 km beneath the surface; damaged the Alaskan Way Viaduct, cracked the state capitol dome in Olympia, and caused $2+ billion in regional damage.
Cascadia Subduction Zone (Entire Pacific Northwest Coast)
Full-margin Cascadia megathrust rupture documented in Native American oral history, drowned ghost forests along the Washington coast, and generated the famous "Orphan Tsunami" recorded in Japan.
Seismic Geology & Soil Amplification in Seattle
Plate boundaries, tectonic kinematics, and local geotechnical ground response characteristics.
Seattle faces a triple seismic threat: shallow crustal faults cutting directly beneath the city center (the Seattle Fault), deep intraplate earthquakes within the subducting Juan de Fuca slab (Wadati-Benioff zone, 40–60 km deep), and catastrophic M 9.0+ megathrust ruptures along the offshore Cascadia Subduction Zone.
Local Soil Profile & Ground Motion Resonance
The Seattle sedimentary basin is over 7 kilometers deep, bounded on the south by the Seattle Fault. This deep basin traps seismic waves, prolonging and amplifying ground motion. Glacial till, fill, and saturated deltaic sediments in Pioneer Square, SODO, and the Duwamish Valley present high liquefaction potential.
Major Active Fault Systems Near Seattle
Seismogenic fault lines, maximum credible magnitudes (MCE), and proximity to the metropolitan center.
Seattle Fault Zone
An east-west trending thrust fault system crossing Puget Sound directly beneath south Seattle, Pioneer Square, and Interstate 90; last ruptured in ~900 AD raising Restoration Point by 7 meters.
Cascadia Subduction Zone (CSZ)
The 1,000 km megathrust interface from Northern California to Vancouver Island; capable of full-margin ruptures with minutes of violent shaking.
South Whidbey Island Fault Zone
Northwest-trending active fault system crossing Whidbey Island and the northern Seattle suburbs of Edmonds and Lynnwood.
Seismic Safety, Observatory & Building Codes
Official seismological monitoring, building construction standards, early warnings, and emergency response.
Frequently Asked Questions About Earthquakes in Seattle
Authoritative answers to common questions regarding seismic risks, building safety, and preparedness in Seattle.
What is the "Really Big One" Cascadia earthquake?▾
The Cascadia Subduction Zone ruptures on average every 400 to 500 years in massive M 8.5–9.2 megathrust earthquakes. Geological records show the last full rupture occurred on January 26, 1700, meaning Cascadia is within its recurring rupture window.
Can the Seattle Fault create a tsunami inside Puget Sound?▾
Yes. Unlike offshore subduction earthquakes whose ocean tsunamis take hours to enter Puget Sound, a vertical thrust rupture on the Seattle Fault directly displaces the Sound floor, generating a localized 3-to-6-meter tsunami that strikes Elliott Bay waterfronts within 3 to 5 minutes.