A hypocenter or hypocentre, also called ground zero or surface zero, is the point on the Earth's surface directly below a nuclear explosion, meteor air burst, or other mid-air explosion. In seismology, a hypocenter of an earthquake is its point of origin below ground; a synonym is the focus of an earthquake.
Monument marking the hypocenter, or ground zero, of the atomic bomb explosion over Hiroshima.
The former hot dog stand nicknamed Cafe Ground Zero in the Pentagon's center courtyard.
Aerial view of the World Trade Center site in September 2001.
A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. The driving reaction may be nuclear fission or nuclear fusion or a multi-stage cascading combination of the two, though to date all fusion-based weapons have used a fission device to initiate fusion, and a pure fusion weapon remains a hypothetical device. Nuclear explosions are used in nuclear weapons and nuclear testing.
A 23 kiloton tower shot called BADGER, fired on April 18, 1953, at the Nevada Test Site, as part of the Operation Upshot–Knothole nuclear test series.