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Monitoring Seismicity to Locate Earthquakes

Earthquake activity is the most consistent sign of volcanic unrest.

This seismogram (courtesy of the Pacific Northwest Seismic Network) shows a series of small debris flow pulses that began at the base of South Tahoma Glacier and flowed down Tahoma Creek on August 13, 2015. (Public domain.)

Seismic networks, used to detect and locate earthquakes, have been a mainstay of Cascade volcano monitoring networks since the 1970s. Seismicity at Cascade volcanoes is monitored in partnership between the Pacific Northwest Seismic Network (PNSN) and the CVO, as well as UNAVCO (through the Plate Boundary Observatory program). There is significant variability in the number of stations at each volcano, which reflects the degree of difficulty in operating seismic stations in remote locations, proximity to population centers, recency of eruptive activity, and land-use permitting restrictions.

Learn more about volcano seismicity:

Seismic station at Three Sisters volcano in Central Oregon. Seismometer in box on the ground with data transmission antenna mounted on pole. (Credit: Moran, Seth. Public domain.)