Glossary
Earthquake, Epicentre and Hypocentre
An earthquake is ground shaking caused by the sudden rupture of a fault. The point at depth where the rupture starts is called the focus or hypocentre. The point on the surface directly above it is the epicentre, the one shown on maps.
An earthquake is called shallow when its focus is less than 70 km deep. These are the most dangerous. Some occur as deep as 700 km, inside plates sinking in subduction zones. Several hundred earthquakes of magnitude 2.5 or more are recorded every day.