Seismograph definition

An instrument for automatically detecting and recording the intensity, direction, and duration of a movement of the ground, especially of an earthquake.

An instrument that detects and records vibrations and movements in the Earth, especially during an earthquake. Most seismographs employ a pendulum mounted within a rigid framework and connected to a mechanical, optical, or electromagnetic recording device. When the Earth vibrates or shakes, inertia keeps the pendulum steady with respect to the movements of the frame, producing a graphic record of the duration and intensity of the Earth's movements. Separate instruments are needed to record the north-south horizontal, east-west horizontal, and vertical components of a tremor. By comparing the records produced by seismographs located in three or more locations across the Earth, the location and strength of an earthquake can be determined.

An instrument that records the intensity and duration of earthquakes and similar tremors.

The definition of a seismograph is a measuring instrument for earthquakes that tracks duration and magnitude.