News Desk: North Korea’s underground nuclear tests appear to have left a prolonged seismic footprint around the country’s Punggye-ri nuclear test site, with scientists detecting 1,399 local earthquakes between 2008 and 2025 and finding evidence that previously quiet faults beneath Mount Mantap were reactivated after the tests.
The findings come from a peer-reviewed study published in the journal Science on September 17, 2026. The research was led by Xingli Fan of Chengdu University of Technology and Kwang-Hee Kim of Pusan National University, along with researchers from institutions in China and South Korea.
Six nuclear tests changed the picture
North Korea conducted six underground nuclear tests at Punggye-ri between 2006 and 2017. The final test, on September 3, 2017, was the country’s largest and produced a seismic event measured at approximately magnitude 6.3.
ThePrint, citing the study, reports an estimated explosive yield of about 160 kilotonnes for the 2017 test. Other reports of the study give a broader estimate of 100–250 kilotonnes, reflecting uncertainty in yield estimates.
The enormous explosion damaged and deformed the surrounding rock. It also caused the summit of Mount Mantap to move upward by roughly 3.5 metres, while a cavity created underground subsequently collapsed.
But the researchers found something more unusual than the immediate effects of the blast.
North Korea’s underground nuclear tests at Mt. Mantap have had long-lasting and delayed effects on the region’s surrounding crust, according to a new Science study, triggering seismic activity that has persisted—and even intensified—for years after the detonations ended.
The… pic.twitter.com/cjOC09Y999
— Science Magazine (@ScienceMagazine) September 17, 2026
Earthquakes did not simply fade away
Scientists analysed 17 years of continuous seismic waveform data, collected between 2008 and 2025 from monitoring stations in South Korea and northeastern China.
Using sensitive seismic-analysis techniques, they identified 1,399 local earthquakes around Mount Mantap. Of these, 955 could be precisely located.
The striking finding was the timing and evolution of the earthquakes.
Instead of seismic activity rapidly declining after the 2017 explosion, researchers found that sustained tectonic activity began roughly three weeks after the test and subsequently increased in both frequency and seismic energy through the end of the study period in 2025.
According to Science, some of the earthquakes occurred 20–30 kilometres from the nuclear test site, showing that the phenomenon extended beyond the immediate blast area.
A region that had been remarkably quiet
The findings become more significant because Mount Mantap is not considered a naturally highly active earthquake zone.
Researchers found that major earthquake catalogues recorded no crustal earthquakes within 50 kilometres of the site between January 1904 and September 2017. Historical records before that period also show very little seismic activity in the immediate region.
However, scientists caution that the absence of historical records does not prove that absolutely no small earthquakes occurred, because seismic monitoring was much less sensitive in earlier periods.
📌 North Korea’s nuclear tests may have triggered over 1,300 earthquakes
Prolonged seismic activity has been detected near North Korea’s Punggye-ri nuclear test site, according to researchers from South Korea and China.
They identified 1,330 earthquakes since North Korea’s 2017… pic.twitter.com/MJOCRpIqHp
— Context 360 (@NewsContext360) September 18, 2026
Two fault structures emerged
The researchers were able to identify a clear pattern when they mapped the 955 precisely located earthquakes.
Rather than being randomly scattered around Mount Mantap, many of the earthquakes progressively clustered along two roughly north-northwest-trending structures. One appears to correspond to the continuation of a previously mapped fault, while the other does not have an obvious surface expression.
This pattern led the scientists to conclude that the earthquakes were associated with reactivation of pre-existing faults rather than being simply conventional aftershocks of the 2017 explosion.
How could a 2017 blast affect earthquakes years later?
The researchers do not suggest that seismic waves from the 2017 explosion continued travelling through the Earth for years.
Instead, their explanation involves long-term changes to the mechanical stresses in the shallow crust.
Repeated nuclear explosions progressively fractured and damaged the surrounding rock. They also redistributed stresses within a crust that already contained faults close to failure. Once the stresses were redistributed, movement along one part of the underground fault system could transfer additional stress to neighbouring sections, potentially causing them to slip later.
The unusual shape and steep topography of Mount Mantap may also have influenced how those stresses were distributed in the shallow crust.
Not every earthquake can simply be attributed to a nuclear test
The study’s conclusion should not be interpreted as meaning that all 1,399 earthquakes were individually and directly caused by nuclear explosions.
Rather, the researchers found a combination of timing, location, increasing seismic activity and fault-related patterns that supports the interpretation that the nuclear tests disturbed an already stressed section of the crust and helped facilitate movement along existing faults.
That distinction is important scientifically because the faults existed before the tests, and scientists cannot conduct a controlled experiment to prove what would have happened in the absence of nuclear testing.
Could a larger earthquake occur?
The researchers have also examined the potential significance of the longer fault-like structure, which extends for roughly 24 kilometres.
If it were a single connected fault and ruptured along its entire length, the researchers estimate that it could theoretically produce an earthquake of approximately magnitude 6.4. However, this is a hypothetical scenario, not a prediction, and the researchers do not say that such an earthquake is imminent.
A longer seismic legacy
The study challenges the conventional expectation that earthquake activity associated with an underground nuclear explosion should rapidly decline after the test.
At Punggye-ri, the evidence instead points to a multi-year process of fault reactivation, in which the effects of repeated explosions interacted with naturally stressed geological structures.
The findings could also have implications for monitoring former nuclear test sites and for interpreting seismic signals during international efforts to detect and verify nuclear explosions. Scientists may need to consider seismic activity occurring years after a nuclear test, rather than focusing only on the immediate aftermath.
