North Korea’s nuclear testing may have triggered hundreds of earthquakes over several years
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Between 2006 and 2017, North Korea conducted six underground nuclear tests at its vast testing site at Mount Mantap in North Hamgyong province. Typically, underground explosions trigger an intense burst of minor earthquakes that die down once testing stops. But geologists have detected far more seismic activity after the final detonation, and it has persisted for years.
The region was previously considered geologically quiet. No crustal earthquakes had been documented within 50 kilometers (31 miles) of the site for more than a century. But all that changed in 2017.
To discover exactly what was happening underground, an international research team led by Xingli Fan from Chengdu University of Technology analyzed 17 years of continuous seismic wave data recorded between 2008 and 2025. The data came from regional monitoring stations in China and South Korea, located 80 kilometers (50 miles) to 200 kilometers (124 miles) away.
They also used a sensitive pattern-matching technique called matched-filter detection to find smaller, hidden tremors that standard earthquake monitoring networks usually miss.
Their findings, published in the journal Science, challenge long-held assumptions about how the Earth responds after an underground blast.
A seismic surprise
Rather than fade away as expected, the seismic activity near Mount Mantap steadily increased and accelerated through 2025. In total, the team detected 1,399 small local earthquakes. “Seismicity at Mt. Mantap continued to increase for years after the final test,” the study authors wrote.
They also mapped the precise locations of 955 of these tremors and discovered they were not randomly located. Instead, they lined up along two distinct, roughly parallel tracks stretching away from the test site.
One of these tracks followed the projected continuation of a fault line geologists already knew about. The second track revealed what appeared to be a completely hidden fault that had never been mapped before. The scientists concluded that the underground explosions had damaged the crust around pre-existing structural weaknesses. But what puzzled them was how explosions that ended years ago were still driving fault movements today.
A mountain under pressure
To explain this long delay, the researchers ran computer models to see how the weight and shape of Mount Mantap affected stresses in the rock beneath it.
They found that the mountain itself played a major role, as its steep, heavy slopes put intense natural pressure on the rock directly beneath it. When the six nuclear explosions blasted through Mount Mantap, they damaged this already stressed rock and weakened the surrounding crust.
The crust did not settle right away. Instead, stresses gradually redistributed through the damaged rock, eventually causing nearby faults to slide years after the blasts stopped. “The Mt. Mantap sequence demonstrates that UNEs [underground nuclear explosions] can produce long-lasting crustal effects in a heterogeneous and critically stressed environment.”
But the findings could have wider implications. The researchers emphasized that these lingering tremors complicate monitoring under the Comprehensive Nuclear-Test-Ban Treaty. This ongoing activity makes it much harder to tell tremors linked to earlier explosions apart from natural earthquakes.
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Publication details
Xingli Fan et al, Nuclear tests at Mt. Mantap have reactivated intraplate faults, Science (2026). DOI: 10.1126/science.adx5917
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North Korea’s nuclear testing may have triggered hundreds of earthquakes over several years (2026, September 18)
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