"The Pacific Northwest (including the part of California north of Cape Mendocino, Oregon, Washington, and part of British Columbia) may be capable of producing a great subduction-zone earthquake of magnitude 8-9. [...] Potential losses in the Pacific Northwest, as a result of either a great subduction-zone earthquake or crustal and (or) intraplate earthquakes near population centers, are expected to be large for a number of reasons. [...] Losses due to earthquakes can be reduced by means of effective mitigation measures, but these mitigation measures cannot be implemented without reliable characterization of earthquake hazards."
U.S. Geological Survey Circular 1067
United States Geological Survey: https://pubs.usgs.gov/