CNN TV says they have confirmation that this was a man made event.

Magnitude 5.1 seismic disturbance recorded in North Korea

Yay, nukes! Can we test our own now, please?

UPDATE:

North Korea says it successfully conducts hydrogen bomb test

Granted, North Korea in the past has proved to be as honest as a Chicago politician, so who knows. A 5.1 magnitude quake equates to *roughly* 0.67 kilotons, which would be one hell of a weak H-bomb, but it’d be in line with the kinda sad nukes the Norks have set off in the past.