Earthquake — Why it happens?

An earthquake is a sudden movement of the earth's crust caused by an abrupt shift of rock along a rupture in the Earth, called a fault.

The crust is the thin outer layer of the Earth and is made of several plates that covers the entire surface of the globe. Since they are all moving they rub against each other in some places, sink beneath each other in others or spread apart from each other.

The sudden movements inside the earth that push against the Earth's fragile crust break the rocks suddenly. This set off a concentric shock waves to move out from that point and releases pressure that has accumulated within the rock. An earthquake is the vibration that radiates out from the breaking rock. Most of the earthquakes occur in the areas where plates collide or try to slide past each other.