Seismograph
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- It is an instrument used to detect and record earthquakes.
- It consists of a metal rod attached to a fixed base.
- During an earthquake, the base moves, but the rod does not move.
- The movement of the base to the rod is commonly transformed into an electrical voltage.
- This record is proportional to the motion of the metal rod relative to the earth, but one can convert it to a record of the absolute motion of the ground.
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