Earthquake

An earthquake is one of the most destructive phenomenon. It is actually the movement or vibration of the uppermost layer of the earth. In other words, it refers to the vibration produced on the surface of the earth which causes various disasters.
It is not more than the vibration of the uppermost surface of the earth due to underground movement which is mostly caused by volcanic activities or fault planes.
Earthquake's measurement is taken by using a instrument called as seismograph. It has very simple mechanism behind its working.