CTBTO's monitoring stations picked up an unusual seismic event in the Democratic People’s Republic of Korea (DPRK) on 3 September 2017 at 03:30 (UTC). Over 100 of our stations contributed to the analysis. The characterization of the event is consistent with a man-made explosion. An initial magnitude estimate of 5.8 has now been revised to 6.1. The event was significantly larger than earlier ones recorded by the system and the location estimate shows that the event took place in the area of the DPRK’s nuclear test site.

This explosion can only be classified as nuclear once corresponding airborne radioactivity is detected. Should traces of radioactivity have been released from the event, typically in the form of the radioactive noble gas xenon, they would need to be transported through the atmosphere to one of the radionuclide stations in the region, detected, sampled and analyzed. Results, if any, can be expected within days or weeks.

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Latest Technical Findings


03 September 2017
CTBTO Press Briefing to media on the announced nuclear test by North Korea

04 September 2017
CTBTO Executive Secretary Zerbo following the resumed 48th Session of the Preparatory Commission

Remarks, Statements and Report

3 Sept. 2017
Statement by the Chairperson
of the CTBTO PrepCom (PDF)

4 Sept. 2017
CTBTO Executive Secretary Zerbo's remarks at the resumed 48th PrepCom session (PDF)

Under-Secretary-General Feltman's remarks to
the Security Council on the nuclear test announced by the DPRK (PDF)