[sahyz-muh-graf, -grahf, sahys-] 
| any of various instruments for measuring and recording the vibrations of earthquakes. |
| seis·mo·graph (sīz'mə-grāf') n. An instrument for automatically detecting and recording the intensity, direction, and duration of a movement of the ground, especially of an earthquake. seis·mog'ra·pher (sīz-mŏg'rə-fər) n., seis'mo·graph'ic (-grāf'ĭk), seis'mo·graph'i·cal (-ĭ-kəl) adj., seis·mog'ra·phy n. |
| seismograph (sīz'mə-grāf') Pronunciation Key
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. |
seismograph
instrument that makes a record of seismic waves caused by an earthquake, explosion, or other Earth-shaking phenomenon. Seismographs are equipped with electromagnetic sensors that translate ground motions into electrical changes, which are processed and recorded by the instruments' analog or digital circuits. A record produced by a seismograph on a display screen or paper printout is called a seismogram. Although originally designed to locate natural earthquakes, seismographs have many other uses, such as petroleum exploration, investigation of the Earth's crust and lower layers, and monitoring of volcanic activity.
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məˌgræf