Shallow (depth less than 25 km) earthquakes with magnitudes up to 7.5 may occur in Washington and Oregon. This type of earthquake occurs within the North American continental crust. A schematic diagram shows the relative postions of the Juan de Fuca and North American Plates. The blue dots show the positions of known large crustal earthquakes in map view and cross-section. These earthquakes include two on Vancouver Island (M 7.3 in 1946 and M 7.0 in 1918), the M 6.8-7.4 North Cascades Earthquake in 1872, and an earthquake on the Seattle Fault 1,100 years ago.

Largest Known Crustal Earthquakes in Washington, Oregon, and British Columbia

Year	Mag.	Loc	Info
900(approx.)	7.4	Seattle Fault	The Seattle Fault Zone - From the USGS
1872	6.8-7.3	North Cascades	From the PNSN
1918	7.0	Vancouver Island	From the Canadian Pacific Geoscience Centre
1946	7.4	Vancouver Island	From "United States Earthquakes" From the Canadian Pacific Geoscience Centre

There are many sources of shallow crustal activity, but which faults are large enough to be a serious hazard is not well understood. Possible sources with recent geologic activity are under investigation.

• Major Faults of the Puget Lowland - Adapted from USGS Map I-1613, Gower and others, 1985
• Active Faults - From the USGS
  • Active Tectonics of the Devils Mountain Fault and Related Structures, Northern Puget Lowland and Eastern Strait of Juan de Fuca Region, Pacific Northwest - U.S. Geological Survey Professional Paper 1643
  • Active Faults in The Puget Lowland - From Sam Johnson of the USGS
  • The southern Whidbey Island fault - From Sam Johnson et al.
• Relative Earthquake Hazards Maps for Oregon - From Oregon DOGAMI
• Fault zone mapping, Portland and Northern Willamette Basins - From the USGS
• Eastern Washington geology and tectonics - from Whitman College - from PNL
• Eastern Washington hazards - The Yakima Fold Belt - seismic monitoring - from PNL
• Eastern Washington hazards - Geologic Hazards at Hanford Reservation - from DOE
• The Blanco Fracture Zone and Offshore seisimicity in the Pacific Northwest