A seismograph is an instrument used to detect and record the vibrations caused by seismic waves as they travel through the Earth. These vibrations can result from natural events like earthquakes or human activities such as explosions. By measuring these movements, seismographs help scientists understand the Earth's internal structure and the dynamics of tectonic plates. Seismographs consist of a mass suspended on a spring, which remains stationary while the ground moves during seismic events. The relative motion between the mass and the ground is recorded on a rotating drum or digital medium, providing valuable data for seismologists to analyze and predict seismic activity.