The instrument used to measure earthquakes is called a seismometer or seismograph. These devices detect ground motions caused by seismic waves generated during an earthquake. Seismometers can record the amplitude and frequency of the waves, providing valuable data about the earthquake's strength, location, and depth. The information collected helps in understanding seismic activity and assessing potential damage. This technology is crucial for earthquake research, safety assessments, and improving early warning systems, ultimately aiding in disaster preparedness and response strategies.