North Korea’s underground nuclear testing appears to have altered the fault system around the Punggye-ri test site, with earthquake activity continuing for years after the largest 2017 detonation, according to a Korean-led research team.
Researchers from Pusan National University and Chinese institutions analyzed seismic observations from Korea and the Mount Paektu region, SBS and Kyunghyang Shinmun reported. The team concluded that the sixth nuclear test in September 2017 reactivated faults around Mount Mantap rather than producing only a short-lived blast response.
The researchers identified a reactivated fault zone at least about 20 kilometers long, according to SBS. Natural earthquakes have continued around the area since the test, suggesting that stress changes from the underground explosion affected an existing geological structure.
A blast effect became a longer geological signal
An underground nuclear test creates an immediate artificial seismic signal, while a reactivated natural fault can continue releasing stress long after the explosion. The study therefore treats the later earthquakes as part of a continuing geological process around the site and gives regional monitoring agencies another factor to consider when interpreting seismic activity near the Korean Peninsula.
SBS reported that the researchers discussed the possibility of an earthquake of magnitude 6.3 or greater if a sufficiently large part of the fault ruptured. That is a hazard estimate rather than a prediction that such an earthquake will occur. The available reporting gives no timetable or probability for a future large event, so continued seismic monitoring will be needed to determine whether the observed fault system is stabilizing or remains capable of a larger rupture.