The May 25 test provided the world with a host of data about North Korea's bomb-making abilities. But only Pyongyang knows if the test was a success.
Washington and Boston
Proliferation experts will want to determine, in particular: the nature of that nuclear device, whether it went off as expected, and whether the North Koreans now intend to produce more fissile material for a potential weapons stockpile.
"There's a tremendous amount we do not know about North Korea," said Richard Bush III, a former US National Intelligence Officer for East Asia, at a Brookings Institution seminar on the nuclear crisis May 27.
On one point, however, there is wide agreement: North Korea's scientists did better this time than in 2006, when they made their first attempt at an underground nuclear explosion.
That one was a fizzle, relatively speaking. This one wasn't.
Scientists at the Lamon-Doherty Earth Observatory in Palisades, N.Y., place the yield of the May 25 blast at between 2.2 and 4 kilotons of TNT – significantly larger than North Korea's 2006 experiment.
The 2006 test still "would have been a disaster if it had gone off in a metropolitan area," says Won-Young Kim, a seismologist at the observatory who specializes in detecting underground nuclear tests. "[But] this one was bigger."
Mr. Kim and his colleagues base their estimate on seismograph readings from several sites in the Pacific and central Asian regions, as well as one in China that was only about 230 miles from the blast zone. The China site is run by a group of international universities and the US Geological Survey.