I fully believe N.Korea has a nuclear device. It would take A LOT of TnT to replicate the seismic activity from that area that Japan and the U.S. Geological Survey has detected everytime N.Korea has "Detonated" a nuclear device. A LOT.
I'm concerned because I am Korean, I was born in Seoul. So this has always been a point of Foreign Policy that I pay close attention to. N.Korea, S.Korea, doesn't matter. Nuclear weapon on the Korean Peninsula need to go. Because if N.Korea can strap one of those things to a missile, S.Korea has to have them, so you have another area of the world ramping up a M.A.D policy which sucks for everyone.