Earthquakes are caused by movement of rock deep within the Earths crust. These sudden movements send vibration waves (called seismic waves) outward in all directions. The waves are felt first at the epicentre and this is where often, most of the damage is caused. Earthquakes are measured according to their magnitude and intensity. Magnitude (energy released from the earthquake) is measured by the Richter Scale. The intensity of an earthquake is measured on the Modified Mercalli Scale. This rates the amount of damage caused by the earthquake.
