It Was (Almost Certainly) A Dud

CNN:

The United States believes North Korea attempted to detonate a nuclear device and that "something went wrong," a U.S. government official told CNN Tuesday.

The official confirmed North Korea informed the Chinese government prior to the test that it would be a 4 kiloton nuclear device.

The official added that the unexpectedly small blast, of a half kiloton or less, indicated "something went wrong."

And via smh.com.au:

Operated by Geoscience Australia, the network is part of an international array of 337 stations linked to the Comprehensive Test Ban Treaty, which Australia signed in 1996.

Half the global system of 15 radiation observation sites can even spot fallout from underground nuclear tests by detecting noble gases - gases with a distinct chemical make-up.

The Government source said although he would not have expected wind to carry fallout from such a tiny underground nuclear test as far as Australia, he was not aware of any monitoring station anywhere that had detected radiation from North Korea.

So either it didn't work, or it was just a bluff faked to look like a nuke test. Or maybe NK scientists are faking out Kim the way Iraqis faked out Saddam on WMDs. Either way, the fallout has been very interesting indeed. Look how Bush has now moved from saying the USA will not accept a nuclear armed NK. Now it's a little different:

"The transfer of nuclear weapons or material by North Korea to states or nonstate entities would be considered a grave threat to the United States."