A seismograph is the device that scientists use to measure earthquakes. The goal of a seismograph is to accurately record the motion of the ground during a quake. If you live in a city, you may have noticed that buildings sometimes shake when a big truck or a subway train rolls by. Good seismographs are therefore isolated and connected to bedrock to prevent this sort of "data pollution."

The main problem that must be solved in creating a seismograph is that when the ground shakes, so does the instrument. Therefore, most seismographs involve a large mass of some sort. 

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The tremors of earthquake produce waves on the surface of the earth . these are called seismic waves .the waves are recorded by an instrument called seismograph. the instrument  is simply a vibrating rod , or a pendulum which starts vibrating when tremor occurs . a pen is attached to vibrating system .the pen records the waves on th paper which moves under it .by studying these waves , scientists can construct a complete map of earthquake .they acan also estimate its power to cause destruction....
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