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The Pacific Northwest Seismic Network, or PNSN, collects and studies ground motions from about 400 seismometers in the U.S. states of Oregon and Washington to monitor volcanic and tectonic activity, gives advice and information, and works to mitigate earthquake hazard.
Damaging earthquakes are well known in the Pacific Northwest, including several larger than magnitude 7, most notably the M9 1700 Cascadia earthquake and the M7.0–7.3 earthquake in about 900AD on the Seattle Fault. The M6.5 1965 Puget Sound earthquake shook the Seattle, Washington area, causing substantial damage and seven deaths. This event spurred the installation of the Pacific Northwest Seismic Network in 1969 to monitor regional earthquake activity.
Earthquakes are recorded frequently on Mount St. Helens, Mount Rainier, and Mount Hood. After successfully using seismic activity to predict the 1980 Mt. St. Helens eruption, monitoring was expanded to other Cascade Mountains volcanoes. The PNSN, in conjunction with the Cascades Volcano Observatory of the USGS, now monitors seismicity at all the Cascade volcanoes in Washington and Oregon. The network was significantly expanded after the damaging 2001 Nisqually earthquake. After a light earthquake on January 30, 2009 the network's emergency notification failed. A magnitude 4.3 earthquake in February 2015 showed that the present architecture of the network results in a significant delay in the early warning notification feature, depending upon the location of the quake, which is the reason the network is being expanded.
The network operates from the Earth and Space Sciences Department at the University of Washington in Seattle, and its data archiving is at the Data Management Center of IRIS Consortium in Seattle. The network is also affiliated with the University of Oregon Department of Geology. It is the second largest of the regional seismic networks in the ANSS (Advanced National Seismic System) and with more data than the networks in the states of Alaska, Utah, Nevada, Hawaii and the New Madrid, Missouri-Tennessee-Kentucky-Arkansas area.
The network is funded primarily by the United States Geological Survey, which stations its own staff on the campus, and the network is managed by UW staff. Additionally, the Department of Energy, the State of Washington, and the State of Oregon provide funding.