Why earthquake happen ???...

The earthquakes occur when the moving plates of the earth’s crust :

1) The plates of earth’s crust are made up of huge rocks having rough edges. Due to their highly rough edges, the movement of two crust plates relative to one another is not smooth. When the two huge plates of earth’s crust slide past one another, they rub against one another ferociously and the rocks on their edges get entangled. Due to entanglement of the rocks at their edges, the two crust plates stop moving for some time. During this time, the plates are still pushing against one another and trying to move but they are not moving. This builds up pressure between the two plates of crust. When sufficient pressure has been built up between the two crust plates, the entangled rocks of the two crust plates break open suddenly with a big jolt. When the entangles rocks of the two crust plates break open suddenly with a big jolt, the earthquake occurs releasing a tremendous amount of energy. This sudden release of tremendous amount of energy produces shock waves (or seismic waves) which make the earth shake. After the earthquake, the plates of earth’s crust start moving again and continue to move until they get entangled again.

2) When the two plates of the earth’s crust moving in opposite directions collide with each other head on, then the ends of these crust plates buckle and fold forming new mountains and causing earthquakes.A tremendous amount of energy is released when the two huge plates of the earth’s crust collide with each other. This tremendous amount of energy sends shock waves (called seismic waves) throughout the earth. When these shock waves reach the surface of earth, the ground starts shaking violently. This shaking of the ground is felt as an earthquake.