Seismological investigation of the 2016 January 6 North Korean underground nuclear test

Abstract

Seismology plays an important role in characterizing potential underground nuclear tests. Using broad-band digital seismic data from Northeast China, South Korea and Japan, we investigated the properties of the recent seismic event occurred in North Korea on 2016 January 6. Using a relative location method and choosing the previous 2006 explosion as the master event, the 2016 event was located within the North Korean nuclear test site, with its epicentre at latitude 41.3003°N and longitude 129.0678°E, approximately 900 m north and 500 m west of the previous event on 2013 February 12. Based on the error ellipse, the relocation uncertainty was approximately 70 m. Using the P/S spectral ratios, including Pg/Lg, Pn/Lg and Pn/Sn, as the discriminants, we identify the 2016 event as an explosion rather than an earthquake. The body-wave magnitude calculated from regional wave Lg is mb(Lg) equal to 4.7 ± 0.2. Adopting an empirical magnitude–yield relation, and assuming that the explosion is fully coupled and detonated at a normally scaled depth, we find that the seismic yield is about 4 kt, with the uncertainties allowing a range from 2 to 8 kt.

Relative Relocations of the North Korean Nuclear Tests From 2006 to 2017 Using the Hi‐Net Array in Japan

“…We repeat this calculation 100 times then obtain the density distribution of the calculated locations (Figure ). The centroid locations of the events are similar to those of determined using the entire Hi‐net array, as well as locations from studies using global stations (Wen & Long, ; Zhang & Wen, ; Zhao et al, , , , ). The 2006 event shows the widest distribution of locations.…”

“…We apply a relative location method to find the relative locations of the events by using the arrival time differences (Selby, ; Wang & Mori, ; Wen & Long, ; Zhang & Wen, ; Zhao et al, ). For each Pn velocity in the range of 7.8–8.3 km/s with intervals of 0.05 km/s, we obtain a source location for each event (Figure f).…”

“…The red star indicates the fixed location of the 2009 nuclear test. The black square, blue circle, red triangle, blue square, and red diamond indicate the respective locations of the nuclear tests determined by Lianfeng Zhao (Zhao et al, , , , ), Murphy et al (), Lianxing Wen Group ( http://seis.ustc.edu.cn/), Selby (), and Wei (), respectively. The black dots indicate the possible source locations used in the grid searching.…”

“…Using seismic data recorded at stations surrounding the explosion sites, the relative locations of the 2006–2017 nuclear tests have been intensively investigated (Murphy et al, ; Selby, ; Wen & Long, ; Zhang & Wen, ; Zhao et al, , , ). Our results agree well with those locations with differences less than 200–400 m on average except for the 2006 event, which shows larger differences of ~1,000 m (Figure ).…”

Accurate relative location estimates for the North Korean nuclear tests using empirical slowness corrections

“…It took place several hundred meters to the North West of the 2009 and 2013 tests, but presumably in the same mountain and with a greater overburden. A recent study using exclusively data from stations at regional distances (Zhao et al 2016) placed the January 2016 explosion approximately 500 m to the West and 900 m to to the North of the have resulted in the more recent tests having taken place in a different body of rock to that in which the 2006 test was carried out. There is no visible infrastructure close to the tunnel assumed to have provided access for the 2006 test, suggesting that this part of the test site has been abandoned.…”