South Korea’s Meteorological Administration (KMA) said a small quake that hit in North Korea’s North Hamgyong province Wednesday was induced by the September 2017 underground detonation of a nuclear device.
The agency said the 2.8-magnitude temblor recorded Wednesday was shallow — only about 12 kilometers (7.5 miles) deep — and struck about 11 kilometers (6.8 miles) east of the Punggye-ri nuclear test site, the only known facility of its kind in North Korea.
However, there were no independent weapons experts present at the event and it is still unclear whether the explosions rendered the tunnels inoperable, or only caused limited damage.
A seismologist at the KMA told CNN that the activity measured Wednesday was almost certainly a natural earthquake rather than an explosion based on the seismic waves detected and the fact that no sound waves were observed.
Because no major fault lines run through North Korea and the quake was recorded so close to the Punggye-ri site, the seismologist said it must be assumed that the quake was a result of the sixth nuclear test.