Concept:A seismograph is the instrument used to detect and record earthquake vibrations.Explanation:An earthquake produces seismic waves that travel through the Earth.The seismograph records these vibrations and helps determine the earthquake's intensity and magnitude.Epicenter is a location on the Earth's surface, not an instrument.A thermometer measures temperature, not seismic activity.Therefore, the correct instrument is the seismograph.Answer:D. Seismograph