A seismograph measures the intensity and duration of seismic waves produced by earthquakes. It consists of a mass that is suspended from a fixed base; during an earthquake, the ground motion causes the mass to move, while the base remains stationary. This movement is recorded as a graph, showing the amplitude of seismic waves over time. Seismographs are essential tools in seismology, allowing scientists to detect and analyze the characteristics of earthquakes, including their epicenter, magnitude, and depth. This information is crucial for understanding seismic activity and assessing potential risks in earthquake-prone areas.