http://en.wikipedia.org/wiki/Ground_burst
Ground burst
A groundburst is the detonation of an explosive device such as an artillery shell, nuclear weapon or air-dropped bomb explodes after hitting the ground. These weapons are set off by (fuses) that are activated when the weapon strikes the ground or something equally hard, such as a concrete building.
http://en.wikipedia.org/wiki/Effects_of_nuclear_explosions
Effects of nuclear explosions
Energy from a nuclear explosive is initially released in several forms of penetrating radiation. When there is a surrounding material such as air, rock, or water, this radiation interacts with and rapidly heats it to an equilibrium temperature (i.e. so that the matter is at the same temperature as the atomic bomb's matter). This causes vaporization of surrounding material resulting in its rapid expansion. Kinetic energy created by this expansion contributes to the formation of a shockwave.
Indirect effects
Earthquake
The pressure wave from an underground explosion will propagate through the ground and cause a minor earthquake. Theory suggests that a nuclear explosion could trigger fault rupture and cause a major quake at distances within a few tens of kilometres from the shot point.
http://dictionary.reference.com/browse/underground
underground
existing, situated, operating, or taking place beneath the surface of the ground.
the place or region beneath the surface of the ground.
Situated, occurring, or operating below the surface of the earth: underground caverns; underground missile sites.
http://en.wikipedia.org/wiki/King_County,_Washington
King County, Washington
[ ROGUE STATE ]King County is located in the [ ROGUE STATE ]Washington. The population in the 2000 census was 1,737,034, and in 2009 was an estimated 1,909,300.
