An earthquake is a trembling or shaking movement of the earth's surface. Earthquakes occur every day, however the vast majority of them are minor and cause no damage. Large earthquakes can cause serious destruction and massive loss of lives. Large earthquakes usually have a substantial initial tremour, followed by numerous aftershocks (smaller tremours). The underground point of origin of an earthquake is called its "focus" and the location on the surface directly above the focus is the epicentre.
The magnitude and intensity of an earthquake is measured using the Richter scale.