Oregonearthquakestoday:liveseismicactivityandCascadiamonitoring

Length

1100 km

Max plausible

M9.2

Return period

~200–500 years; last full rupture Jan 26 1700 (~325 years ago)

The Juan de Fuca plate subducts beneath the North American plate along a 1,100 km offshore fault from northern California to southern British Columbia. The last full-margin rupture occurred January 26, 1700, generating a trans-Pacific tsunami. At an average return period of ~240 years, the fault is statistically overdue for its next major event. A full-margin M9.0+ rupture would produce shaking lasting 3–5 minutes across Oregon and generate a local tsunami arriving on the coast within 15–30 minutes.

Length

40 km

Max plausible

M7.0

Return period

Unknown; last identified rupture ~1850 based on paleoseismic trench evidence

A blind thrust fault running beneath west Portland. Paleoseismic trench studies in the early 2000s identified evidence of a large rupture approximately 1,000–3,000 years ago. A M7.0 earthquake on the Portland Hills Fault would directly underlie Portland's dense urban core, potentially causing more casualties than a distant Cascadia M9 depending on time of day and building age.

Length

70 km

Max plausible

M7.0

Return period

Unknown

A northwest-trending fault running from the Portland metro area through the northern Oregon Coast Range. The Gales Creek Fault is a mapped active fault in DOGAMI's statewide fault database and contributes to seismic hazard assessments for the Portland metropolitan area and the Coast Range corridor.

Return period

Active — ongoing microseismicity

An offshore transform fault zone off Cape Blanco in southern Oregon that intersects the Cascadia Subduction Zone. Cross-margin faulting at Cape Blanco contributes to stress partitioning in the southern Cascadia segment and is associated with recurring moderate earthquakes near the Mendocino Triple Junction.

United States Geological Survey

National (USA)

Primary catalog for Oregon earthquakes via the ANSS Pacific Northwest network. Publishes ShakeMap, Did You Feel It reports, and the Cascadia long-term hazard assessments.

Pacific Northwest Seismic Network (University of Washington + University of Oregon)

Pacific Northwest (OR, WA)

Operates the densest seismometer network in Cascadia. Issues real-time earthquake notifications for Oregon and Washington, feeds USGS ANSS catalog, and monitors volcanic tremor at Mount Hood and other Cascade volcanoes.

Oregon Department of Geology and Mineral Industries

State (Oregon)

Publishes Oregon-specific tsunami inundation maps, Cascadia scenario studies, URM building inventories for Portland, and school seismic retrofit programs.

Oregon Office of Emergency Management

State (Oregon)

State-level Cascadia response planning agency. Coordinates 'Cascadia Rising' multi-agency exercises and maintains Oregon's FEMA Region 10 earthquake preparedness plans.