Example Volcanic Seismic Signatures
Seismometers can detect rapid ground motion caused by different types of phenomena, including wind, a herd of elk or hovering helicopter, volcanic explosions, snow and rock avalanches, lahars, and earthquakes. Just as we have unique handwriting signatures, each type of ground-shaking event usually generates a unique seismic "signature" that we can learn to recognize and identify as having been "written" by a specific event. Often, we need several seismic signatures of the same event from different seismometers located at increasing distance from the volcano to interpret the ground-shaking event accurately. We can improve our interpretation of a volcano's many seismic signatures when we have direct visual observations of the volcano with which to compare with the recordings.
Seismic Signatures From Mount Rainier, Washington
Based on nearly 30 years of seismic monitoring, the seismic signatures above represent the most common events that cause the ground to vibrate at the volcano. The overall shape of each seismic signature is easy to see by comparing the amplitude (height of waveform), frequency (width from peak to peak within waveform), and duration (length of waveform) of each signature. The "tic" marks on each signature represent 1 minute in time. Earthquake activity at Mount Rainier volcano is monitored by scientists of the Pacific Northwest Seismic Network, University of Washington, with support from the USGS.