An AFP report describes the technologies and methods used by the CTBTO to detect nuclear testing and explains how the CTBTO’s verification system detected the two previous nuclear tests by North Korea in October 2006 and May 2009. [comment: since then our network’s density has significantly increased, see interactive map].
Some 270 stations and laboratories around the world monitor seismic and other activity under the Comprehensive Test Ban Treaty Organisation, making up about 80 per cent of the total envisioned under the 1996 UN treaty. [comment: we’ve already crossed the 85%]
Seismic detention put the May 25, 2009, test at around 4.5 magnitude with an explosive yield of a few kilotons, well below that of the nuclear bombs which the United States dropped on Japan in 1945. North Korea’s 2006 test was detected at magnitude 4.1.
Two weeks after the 2006 test, the isotope Xenon-133 was detected across the Pacific Ocean in the northern Canadian city of Yellowknife. But the North Koreans were successful in 2009 in sealing off the test site.