In terms of nuclear explosions and other large bombs, the term ground zero (sometimes also known as surface zero as distinguished from ) describes the point on the Earth's surface closest to a detonation. In the case of an explosion above the ground, ground zero refers to the point on the ground directly below the nuclear detonation and is sometimes called the hypocenter. Generally, it is also used in relation to earthquakes, epidemics, and other disasters to mark the point of the most severe damage or destruction.