The Comprehensive Test Ban Treaty Organization (CTBTO) announced this week that the organization is able to detect seismological activity in North Korea "within minutes" of an explosion. Following North Korea's previous nuclear tests in 2006 and 2009, the CTBTO was able to determine "within a couple of hours" of each event that they were explosions, not earthquakes.
According to Annika Thunborg, a spokeswoman for the CTBTO, it will take the organization several days to verify that the event was a nuclear test explosion, as opposed to an exceptionally large conventional explosion. This confirmation will come from a detailed analysis of the International Monitoring System's seismological data and information from one or more of the organization's 62 operational radionuclide stations.
For more information on the CTBTO's ability to detect a North Korean test, see: http://newsroom.ctbto.org/.
North Korea has covered the entrance of a tunnel at its nuclear test site to thwart foreign intelligence services' ability to predict the timing of its next nuclear test. For more information, see: