An instrument that measures earthquakes is called a seismometer or seismograph. These devices detect and record the vibrations caused by seismic waves generated during earthquakes. Seismometers consist of sensitive sensors that can pick up ground motion, translating this data into graphical representations known as seismograms. By analyzing these records, scientists can determine the magnitude, duration, and epicenter of an earthquake. This information is critical for understanding seismic activity and helps in earthquake preparedness, response, and research into tectonic processes, thereby contributing to public safety and scientific knowledge.