The term Groun Zero may be used to describe the point on the earth's surface where an explosion occurs. In the case of an explosion above the ground, Ground Zero refers to the point on the ground directly below an explosion (see hypocenter). The term has often been associated with nuclear explosions and other large bombs, but is also used in relation to earthquakes, epidemics and other disasters to mark the point of the most severe damage or destruction. Damage gradually decreases with distance from this point.