What is the name of the instrument that records earthquake waves?

The instrument that records earthquake waves is a seismograph. It detects ground motion and produces a record called a seismogram.

A traditional seismograph uses a heavy, suspended mass that tends to remain relatively still while the ground and instrument frame move during an earthquake. The difference in motion is recorded mechanically or electronically. Modern instruments are usually called seismometers, although “seismograph” remains the familiar quiz answer.

Seismic waves include fast P-waves, slower S-waves, and surface waves. Scientists compare the arrival times of these waves at several stations to estimate an earthquake’s location. The wave record also helps researchers calculate magnitude and study Earth’s interior.

A seismograph is not the same as a barometer, which measures air pressure, or a thermometer, which measures temperature. A seismogram is the record; the seismograph is the recording instrument.