When North Korea conducts an underground nuclear test, a vast
array of global sensors will detect the detonation almost
immediately. But key questions about the size of the explosion,
the number of bombs tested, or whether plutonium or uranium was
used, may never be answered conclusively, analysts say. North
Korea appears to have conducted an underground nuclear bomb test
Tuesday, as the U.S. Geological Survey reported a seismic
disturbance centered near the site of the secretive regime's two
previous nuclear tests. The area around the reported epicenter
of the magnitude 4.9 disturbance has little or no history of
earthquakes or natural seismic hazards, according to U.S.
Geological Survey maps. Despite international condemnation,
North Korea has said it would conduct its third underground
nuclear test. A third nuclear test could enable North Korea the
technical data needed to miniaturize a warhead, according to a
recent paper in the "Bulletin of the Atomic Scientists." Coming
on the heels of December's succes