It's been on the news, leaders have talked about what to do now. South Korea talk about the crazy people up north (did they forget the crazy people in the East?.. Japan).
An unusual geological event was reported in North Korea on Tuesday, 12 February, 2013 at 04:00 (04:00 AM) UTC. The epicenter of the seismic activity, which was only one kilometer below the Earth’s surface, was close to the North’s known nuclear test site. The seismic activity recorded an M5.1 earthquake.
U.S. intelligence officials say North Korea's nuclear test yielded an explosion of "approximately several kilotons." In a statement Tuesday, the Office of the Director of National Intelligence said North Korea "probably conducted an underground nuclear explosion in the vicinity of P'unggye." It said the explosion yield was "approximately several kilotons" and that analysis of the event is continuing. South Korea's Defense Ministry said it detected an estimated explosive yield of 6-7 kilotons.