An earthquake is the vibration felt when energy is released by the sudden displacement of rock along faults, or large fractures, within the Earth's crust.

Types of faulting that leads to the developement of earthquakes.

Most earthquakes can be explained by plate tectonics and the elastic rebound theory. The theory was proposed by H.F. Reid of Johns Hopkins University in 1906. It says that the constant motion of rocks along one side of the fault boundary causes the rocks on the other side to bend, building up and storing elastic energy. Eventually the frictional forces holding the rocks together are overcome and the rocks break at the weakest point along the fault line, known as the focus. The deformed rock experiences slippage, snapping back to its original position. The energy released by this break and slippage causes earthquake vibrations.