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The Pacific Northwest (PNW) is an active seismic area with three distinct types of earthquakes. Major deep earthquakes recur every 30 years or so in western Washington. Subduction-zone earthquakes, which can be as large as magnitude 9.0 (M9.0), recur every few hundred years on a long offshore fault that parallels the coast of Washington and Oregon. Shallow crustal faults within the continental plate are a hazard to major urban centers from Seattle to Portland. Although recurrence times are not known, crustal earthquakes are a possibility almost anywhere in Washington and Oregon, including areas east of the Cascades such as Wenatchee, Yakima, and Walla Walla. Crustal earthquakes also precede volcanic outbursts and were used to predict eruptions at Mount St. Helens in the 1980s.
Each year, the PNSN records several dozen felt earthquakes and thousands of smaller earthquakes—ongoing reminders of the earthquake hazards in Washington and Oregon.
The Network: PNSN's Earthquake Monitoring Equipment uses several different types
of sensors that measure ground motion: accelerometer 
; seismometer (3 components)
; seismometer (1 component) 
; Cascade volcanoes 
.
To monitor earthquake and volcanic activity across the Pacific Northwest, the University of Washington and the University of Oregon cooperatively operate the PNSN. Beginning in 1969 with five seismometers, the PNSN has grown to more than 200 seismograph stations distributed across the region. At the heart of the PNSN is an information and operations center, located at the University of Washington Department of Earth and Space Sciences, which provides rapid earthquake information to emergency responders, the press, and the public and high-quality data to engineers. The PNSN is sponsored by the U.S. Geological Survey (USGS), the U.S. Department of Energy, and the State of Washington.
Deep earthquakes (40 miles below the Earth's surface) are within the subducting
Oceanic plate as it bends beneath the Continental plate. The largest deep Northwest
earthquakes known were in 1949 (M7.1), 1965 (M6.5), and 2001 (M6.8).
Shallow earthquakes (less than 15 miles deep) are caused by faults in the North
American Continental plate. The Seattle fault produced a shallow magnitude
7+ earthquake 1,100 years ago. Other M7+ earthquakes occurred in 1872, 1918,
and 1946.
Subduction earthquakes are huge quakes that result when the boundary
between the Oceanic and Continental plates ruptures. In 1700, the most recent
Cascadia Subduction Zone earthquake sent a tsunami as far as Japan.
Mount St. Helens/other Cascade volcanoes.
Automatic maps and event information are available within minutes online at the PNSN Web site http://www.pnsn.org/recenteqs and the Earthquake Hazards Program Web site http://earthquake.usgs.gov/, which displays earthquake locations nationwide.
Instrumentally measured shaking intensity. Fast information on strong shaking in urban areas helps get emergency response to the right places. http://www.pnsn.org/shake/ and http://earthquake.usgs.gov/shakemap/
Automated notifications of earthquakes through e-mail, pager, or cell phone. Rapid information and updates to first responders, and resources for media and local government.http://earthquake.usgs.gov/products/services.html Links to preparedness information http://earthquake.usgs.gov/hazards/prepare.html
Real-time waveform displays from 60 stations are available online 24 hours a day. http://www.pnsn.org/WEBICORDER/GREEN/ and http://earthquake.usgs.gov/activity/helicorders.html
Human reports of shaking. Report your earthquake experience and see the map of shaking reports. http://pasadena.wr.usgs.gov/shake/pnw
Hazard maps identify the areas of the country that are most likely to experience strong shaking in the future. Zip code or latitude-longitude lookup is available. http://eqhazmaps.usgs.gov/
Online catalog search and downloadable information and technical data. http://www.quake.geo.berkeley.edu/anss/catalog-search.html
Information about earthquake hazards, historical seismicity, faults and more is available for different regions of the country, and by State. http://www.pnsn.org/HAZARDS/ and http://neic.usgs.gov/neis/states/states.html
[Photo by George Thomas, PNSN]
Seismometers in Schools—Schools throughout Washington and Oregon host seismometers
and view the data immediately on the Web. The PNSN also provides onsite and
online Lab tours.
Earthquakes for Kids—For students and teachers, with an
earthquake glossary, learning links, science fair ideas, and much more! http://www.pnsn.org/OUTED/ and http://earthquake.usgs.gov/4kids/
[Photo by Seth Moran, USGS]
Cascade volcanoes: Updates on earthquake activity at Mount Adams, Mount Baker, Crater Lake, Glacier Peak, Mount Hood, Mount Rainier, Mount St. Helens, and Three Sisters. http://www.pnsn.org/INFO_GENERAL/volcanoes.html
Pacific Northwest Seismograph Network
University of Washington
Dept. of Earth and Space Sciences
Box 351310
Seattle, WA 98195-1310
http://www.pnsn.org/
Earthquake Hazards Program
U.S. Geological Survey
Golden, CO 80401
http://earthquake.usgs.gov/
Written by Ruth Ludwin
Graphics and layout design by Eleanor M. Omdahl and Lisa Wald
This Fact Sheet is available online at https://pubs.usgs.gov/fs/2004/3073/Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually impaired. This information provides tools to help make PDF files accessible. These tools convert Adobe PDF documents into HTML or ASCII text, which then can be read by a number of common screen-reading programs that synthesize text as audible speech. In addition, an accessible version of Acrobat Reader 6.0, which contains support for screen readers, is available. These tools and the accessible reader may be obtained free from Adobe at Adobe Access.
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