A seismometer records waves created by an earthquake, and anything else that causes shaking of the Earth, like cars and even you walking near the instrument.
A borehole seismometer is buried 200 meters (650 feet) beneath the Earth's surface so that it only records earthquake vibrations. This helps scientists detect very small earthquakes.
The squiggly lines in the image below are the earthquake waves recorded by several borehole seismometers across the western United States during a magnitude 6.0 earthquake that occurred in Wells, Nevada in 2008. PBO has installed over 75 Borehole seismometers as part of EarthScope.