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A nearby seismograph station records an elk running. Even a sensitive station cannot detect this type of surface thumping at a distance.
A nearby seismograph station records the helicopter down draft, landing, and the foot fall as geologists walk away from the craft.
Falling rock, common in a volcanic crater, creates a seismogram with a slow build up, a rumbling peak, and a tapering off.
Rock Break Earthquakes
As a volcano responds to stress in the massive edifice, rock breaks sending short-duration sharp seismic signals.
Here we track the fastest P and S waves as they are refracted along a faster layer at depth. P and S waves travel faster than the slower surface waves which had a more-direct path.
P and S waves are refracted and speed up in faster layers at depth. Even from long distances, teleseismic (more than 500 km away) earthquakes are recorded by sensitive seismograph stations.
Animations and videos are made in partnership with Earthscope, USGS, and Volcano Video & Graphics.
Please send feedback to Jenda Johnson.