Helicorders on display at the University of Alaska Fairbanks Geophysical Institute ~2003. Helicorders record seismic signals from seismometers by drawing lines on paper wrapped around a rotating drum. Each line of data represents a specific amount of time. Photo by Michael Doukas, USGS.
Credit: Image courtesy of AVO/USGS.Use Restriction: Please cite the photographer and the Alaska Volcano Observatory / U.S. Geological Survey when using this image.
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