DESCRIPTION:
Oregon Earthquakes and Seismicity

Earthquakes occur when rocks break suddenly in response to various geologic forces. Magma moving in the Earth's crust may create sufficient force to produce volcanic earthquakes. More common, however, are tectonic earthquakes, which periodically strike parts of Oregon. These earthquakes, the result of fault movements driven by regional crustal stresses, typically have no direct connection to magma movement. Regardless of type, earthquake size is reported by magnitude, and many scientists and media describe earthquakes by the well-known Richter magnitude scale. ...

Tectonic earthquakes occur periodically in south-central and southeast Oregon, and they are capable of exceeding the magnitude of volcanic earthquakes. An example is the Klamath Falls earthquakes, a swarm that began in September 1993 with two large earthquakes of magnitude 5.9 and 6.0 that killed two people and and caused $7.5 million in property damage. Aftershocks as large as magnitude 5.1 continued to disturb residents for as much as six months. These earthquakes had no connection with volcanic processes.

Information on Pacific Northwest earthquake activity and hazards is provided by the Pacific Northwest Seismic Network (PNSN) which operates seismograph stations and locates earthquakes in Washington and Oregon. The PNSN is operated jointly by the University of Washington, the University of Oregon, and Oregon State University, and is funded by the U.S. Geological Survey, the Department of Energy, and the State of Washington. The PNSN is based at the Geophysics Program of the University of Washington in Seattle, and is a member of the Council of the National Seismic Systems (CNSS), a group of regional network operators who cooperate to locate and catalog earthquakes throughout the United States.

In addition to locating regional earthquakes, the Pacific Northwest Seismic Network (PNSN), in cooperation with the Cascades Volcano Observatory, is also responsible for monitoring seismic activity at volcanoes in the Pacific Northwest. The PNSN currently operates seismometers on or near Mount Adams, Mount Rainier, Mount St. Helens, Mount Hood, Mount Baker, Three Sisters, and Crater Lake.

• Mount Hood Seismicity Menu
• Three Sisters Seismicity Menu
• Crater Lake Seismicity Menu

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