Earthquakes are natural geologic phenomena caused by the sudden and rapid movement of a large volume of rock. The violent shaking and destruction caused by earthquakes are the result of rupture and slippage along fractures in Earth's crust called faults. Larger quakes result from the rupture of larger fault segments. The origin of an earthquake occurs at depths between 5 and 700 kilometres, at the focus. The point at the surface directly above the focus is called the epicenter (figure 8. 2).