Based on the similarity of the seismic data between 9 September 2016 event and North Korea’s previous nuclear tests, we confirm that 9 September 2016 event is a nuclear test in nature. We have determined that North Korea’s 9 September 2016 nuclear test occurred at 00:30:01.366 UTC, (9:00:01.366 local time), 9 September 2016, at the location of (41°17'54.60''N, 129°4'40.80''E), with an estimated yield of 17.8±5.9 kt. The geographic precision of the location determination is 110 m. North Korea’s 9 September 2016 test and its three previous tests (2016/01/06, 2013/02/12 and 2009/05/25) are located several hundred meters apart, beneath a same mountain. The estimated yield of 9 September 2016 test is higher than that of its previous tests (11.3±4.2 kt for 2016/01/06 test, 12.2±3.8 kt for 2013/02/12 test, and 7.0±1.9 kt for 2009/05/25 test). Figure 1 shows the determined location and yield of North Korea's 9 September 2016 nuclear test, along with the locations and yields of its previous tests.
Figure 1. (a) Best-fitting location of 9 September 2016 test (star labeled as 2016/09/09) relative to the location of 2009 test (star labeled as 2009/05/25). The black ellipse represents the 95% confidence ellipse for 9 September 2016 test location based on the chi-square distribution. (b) Locations (circles, with the sizes of symbols proportional to their yields (labeled blue)) and origin times (labeled red) of 2006, 2009, 2013, and two 2016 tests plotted on a Google Earth map.
North Korea’s 9 September 2016 nuclear test site is pinpointed by deriving relative location of North Korea’s 2016/09/09 and 2009/05/25 nuclear tests and using the previously determined location of the 2009 nuclear test, while its yield is estimated based on the relative amplitude ratios of the Lg waves recorded for both events, the previously determined Lg-magnitude of 2009 nuclear test and burial depth inferred from satellite imagery. Figure 2 shows the seismic stations and seismic data used to relocate the nuclear test. The seismic data come from a seismic station in China (MDJ) of the Global Seismographic Network, jointly operated by the Incorporated Research Institutions for Seismology and China Earthquake Administration and some seismic stations in China and Japan.
Figure 2. Map showing North Korea’s 2009/05/25 and 2016/09/09 nuclear test sites (red star), seismic stations (triangles) that recorded high-quality waveforms for both tests, and observed vertical components of seismic waveforms. Seismic waveforms are self-normalized and labeled with station names and the year of the test.
♦ For 9 September 2016 event information at USGS: click here.
♦ For 9 September 2016 event information reported by CTBTO: click here.
Links to our research about North Korea's previous nuclear tests:
♦ For the seismic results of the North Korea's 6 January 2016 nuclear test, click here.
♦ For the scientific publication of the study of North Korea's 2013 nuclear test, click here.
♦ For the scientific publication of the study of North Korea's 2010 nuclear test, click here.
♦ For general introduction of the study and our previous study related to North Korea's 2009 nuclear test, click here.
♦ For the scientific publication of the study of North Korea's 2009 nuclear test, click here.
♦ For more information about Professor Lianxing Wen: http://geophysics.geo.sunysb.edu/wen/
Copyright University of Science and Technology of China, 2016.