Seismologists monitor North Korea's nuclear blasts

Seismologists continue to estimate the strength of North Korea’s most recent nuclear test, using a global system to detect such blasts. Though there was concern in the past that smaller explosions could go unnoticed if shielded in porous rock caverns, improved monitoring systems prevent blasts from escaping detection. Edwin Lyman of the Ploughshares-funded Union of Concerned Scientists comments, "I would assume their ultimate goal would be that they want the world to think they could deliver a device like this on a missile." After testing six short-range missiles last week, Lyman finds it unlikely that North Korea took steps to muffle their underground nuclear test blast. "It's not in their interest to conceal what they actually achieved," he says.