North Korea's nuclear tests have activated dormant faults and triggered earthquakes, scientists say
North Korea has conducted at least six large-scale underground nuclear weapons tests at the Punggye-ri test site near Mount Mantap in North Hamgyong Province. A new study has shown that the effects of the last explosion in 2017 may have lasted much longer than previously thought.
According to the researchers, seismic activity in the Mount Mantap area continued for years after the last nuclear test.
A group of scientists from Chinese universities recorded earthquakes along several fault lines that had previously remained relatively quiet. The study period spanned from September 2017 to May 2025.
North Korea’s most recent nuclear test at that time took place on September 3, 2017. American seismologists recorded an underground event with a magnitude of 6.3.
Meanwhile, on September 23, 2017—approximately three weeks after the explosion—a new series of seismic events began in the region, which continued intermittently until May 2025—the last month for which the researchers collected data.
The scientists analyzed data from seismic sensors located in China and South Korea. In total, over the study period, they identified 1,399 local seismic events, which was an unusually high number for this region.
“The gradual increase in both the frequency of earthquakes and the rate of seismic moment release indicates that the Earth’s crust has not returned to a state of equilibrium since the last eruption,” the researchers note.
According to them, seismic activity “gradually spread as existing faults became more active.”
Researchers estimate the yield of the nuclear device tested by North Korea in September 2017 at 100–250 kilotons in TNT equivalent.
This is significantly more powerful than the atomic bomb the U.S. dropped on Hiroshima at the end of World War II. Depending on the yield estimate, the device tested by North Korea could have been approximately 7–17 times more powerful.
The lead author of the study was geophysicist Xingli Fan from the Key Laboratory of Earth Science and Information Technology at Chengdu University of Technology.
Together with his colleagues, he analyzed seismic records from China and South Korea to determine how the underground nuclear explosion affected geological structures in the Mount Mantap area.
The link between underground nuclear explosions and seismic activity has been known since the Cold War. However, previous studies of tests at test sites in the United States and the former Soviet Union showed that the seismic events caused by the explosions were mostly short-lived—lasting days or weeks—and remained concentrated near the epicenter. Afterward, activity typically returned to normal levels.
In the Mount Mantap region, the situation turned out to be different. Researchers consider the prolonged intensification and spread of seismic activity to be anomalous for the aftermath of underground nuclear tests.
According to their assessment, the underground explosions may not only have triggered short-term tremors but also delayed the reactivation of intraplate faults for years.
The detected seismic activity is significant not only for seismic safety in the northeastern part of North Korea but also for international monitoring of nuclear tests.
Scientists warn that earthquakes occurring years after a nuclear explosion can complicate the determination of the causes of new seismic events and blur the line between the effects of the explosion and natural tectonic processes.
“Seismic activity occurring years after a detonation can make it difficult to determine the origin of events and blur the distinctions between blast-related and tectonic phenomena,” the study’s authors noted.
In their view, this is why long-term monitoring and detailed analysis of seismic activity near former nuclear test sites are necessary.
Gizmodo reports on this.
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