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.
Image courtesy of AVO/USGS.Please cite the photographer and the Alaska Volcano Observatory / U.S. Geological Survey when using this image.
Full Resolution.