North Korea's underground nuclear tests caused long-lasting changes to the Earth's crust around its Punggye-ri test site, reactivating dormant faults and triggering seismic activity years after the explosions ended, according to new research.
The peer-reviewed study, published Thursday in the journal Science, analyzed 17 years of seismic data recorded in South Korea and northeastern China between 2008 and 2025.
Researchers identified 1,399 local earthquakes around Mount Mantap, where Pyongyang conducted six underground nuclear tests between 2006 and 2017.
The study found seismic activity accelerated after North Korea's sixth and largest nuclear test in September 2017, rather than fading within days or weeks as typically expected following underground explosions.
That test produced a magnitude 6.3 seismic event and had an estimated yield of 100 to 250 kilotons, according to the study.
Earthquakes began increasing about three weeks afterward and continued growing in frequency and magnitude through 2025.
Researchers found the earthquakes increasingly clustered along two roughly north-northwest-trending fault structures.
They concluded that repeated nuclear explosions progressively damaged the shallow crust and redistributed stress, allowing faults already close to failure to reactivate gradually.
The research was jointly led by Xingli Fan of Chengdu University of Technology and Kwang-Hee Kim of South Korea's Pusan National University.
North Korea conducted its first nuclear test on Oct. 9, 2006, at Punggye-ri and carried out five more tests between 2009 and 2017.
Five days after the first test, the UN Security Council unanimously adopted Resolution 1718, imposing sanctions that included an arms embargo, asset freezes, and travel restrictions targeting people involved in Pyongyang's nuclear program. The sanctions regime was subsequently expanded in response to further nuclear tests and ballistic missile activity.
Following the sixth nuclear test in 2017, the Security Council imposed additional sanctions, including restrictions on North Korean textile exports, natural gas supplies, and overseas workers.
