Mount Mantap's earthquakes kept accelerating for eight years after North Korea's last test
An international team detected 1,399 small earthquakes in 17 years of continuous recordings from stations in China and South Korea, and the 955 they could locate trace two faults, one of which was never on a map.
The Scientist · Science desk
What happened
- Before 2017, the ground around Mount Mantap was quiet enough that no crustal earthquake had been documented within 50 kilometres of the North Korean test site for more than a century.
- North Korea conducted six underground nuclear tests beneath the mountain, in North Hamgyong province, between 2006 and 2017.
- A team led by Xingli Fan of Chengdu University of Technology detected 1,399 small local earthquakes in 17 years of continuous data and found the rate still climbing through 2025.
- The 955 events the team could locate lie along two roughly parallel tracks running away from the site, one of them extending a fault geologists had already mapped.
- The catalogue came from stations in China and South Korea between 80 and 200 kilometres away, with matched-filter pattern matching used to recover tremors standard networks miss.
Why it matters
- What it limits constraint Treaty verification in this region loses its easy background: small events near Punggye-ri now have to be argued into one category or the other, and that burden falls on the analysts doing attribution.
- Who's exposed exposure Rock fractured enough to stop holding radioactive gas turns any further work at the complex into a release question as well as a detection one.
- What it sets up precedent The paper's claim is general, so other test sites in heterogeneous, critically stressed crust become places to look for sequences that outlast the shooting by years.
- Who has to decide decision The collapse takes the peak itself out of use, so a future North Korean test has to be sited on other ground inside Punggye-ri.
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The explanation the team offers starts with the mountain itself. Mount Mantap's steep, heavy slopes press down on the rock beneath the peak, and the group's computer models put that rock under intense stress before any device went into it [13]. Six explosions damaged that already stressed rock and weakened the crust around it [14]. The 2017 test, with an estimated yield of 100 to 250 kilotons of TNT, effectively collapsed the top of the mountain [18][23]. Stress then redistributed through the damaged volume slowly, and faults slid years after the blasts stopped [14]. The authors wrote that the Mount Mantap sequence shows underground nuclear explosions can produce long-lasting crustal effects in a heterogeneous and critically stressed environment [15].
Kwang-Hee Kim, a seismologist at South Korea's Pusan National University and a co-author, said repeated underground nuclear tests have progressively disturbed and damaged the surrounding rock and changed the stresses acting on pre-existing faults [16]. Kim said the 2017 test did the most damage, and that once faults on the mountain were disturbed it started a domino effect [17].
The causal argument leans on timing and on geometry. Recorded activity grew in both frequency and magnitude after 3 September 2017 [3], and the located events line up along two tracks [11]. The century of documented quiet is the softer support [7]. Matched-filter detection pulls out small tremors that standard networks miss [10], so a historical record assembled without it is not a like-for-like background. The comparison inside the study is stronger: same stations, same method, 2008 through 2025 [8][9]. That catalogue opens two years after the first test [27].
The team detected 1,399 events and located 955 of them, about 68 percent, which leaves 444 detections with no mapped position [1][11][26]. Contributing stations sit between 80 and 200 kilometres from the site [9]. So the previously unmapped fault is drawn from roughly two-thirds of the catalogue [12].
The record does not show how large the sequence can get. "The phenomena they've identified and documented is a bit surprising," said Paul Richards, a Columbia University seismologist who was not involved in the work [19][20]. He called the situation "potentially dangerous" and asked, "Will it lead to even bigger earthquakes?" [21].
I would not call the crust under Mount Mantap permanently destabilised on this evidence. The paper's own term is long-lasting [15], and the record covers about eight years after the last test [28]. What the faults do after 2025 is outside it.
What to watch
- Whether the 444 detections that could not be located are placed later, which would test the two-track fault geometry against the full catalogue.
- Whether monitoring bodies revise the discrimination baseline they use for events near Punggye-ri in published bulletins.
- A test at another underground site in the Punggye-ri complex would put the stress model to work on ground that has not been shot before.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence76
- Adoption
- Not scored
- Hype gap+14
- Incentives33
- Confidence68
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
The team detected 1,399 small local earthquakes; rather than fading, seismic activity near Mount Mantap steadily increased and accelerated through 2025.
- [2]
"Seismicity at Mt. Mantap continued to increase for years after the final test," the study authors wrote.
- [3]
Almost 1,400 earthquakes occurred at Mount Mantap between 2008 and 2025, and they have increased in frequency and magnitude since 3 September 2017, the date of the last known nuclear test there.
- [4]
North Korea conducted six underground nuclear tests between 2006 and 2017 at its testing site at Mount Mantap in North Hamgyong province.
- [5]
The study was published in Science on 17 September: Xingli Fan et al, "Nuclear tests at Mt. Mantap have reactivated intraplate faults", Science (2026), DOI 10.1126/science.adx5917.
- [6]
The researchers emphasised that the lingering tremors complicate monitoring under the Comprehensive Nuclear-Test-Ban Treaty, making it much harder to tell tremors linked to earlier explosions apart from natural earthquakes.
- [7]
The region around the site was previously considered geologically quiet: no crustal earthquakes had been documented within 50 kilometres of the site for more than a century.
- [8]
An international research team led by Xingli Fan of Chengdu University of Technology analysed 17 years of continuous seismic wave data recorded between 2008 and 2025.
- [9]
The data came from regional monitoring stations in China and South Korea located 80 kilometres to 200 kilometres from the site.
- [10]
The team used matched-filter detection, a pattern-matching technique, to find smaller hidden tremors that standard earthquake monitoring networks usually miss.
- [11]
The team mapped the precise locations of 955 of the tremors and found they were not randomly located but lined up along two distinct, roughly parallel tracks stretching away from the test site.
- [12]
One track followed the projected continuation of a fault line geologists already knew about; the second revealed what appeared to be a completely hidden fault that had never been mapped before.
- [13]
Computer models of how the weight and shape of Mount Mantap affect stresses in the rock showed the mountain's steep, heavy slopes put intense natural pressure on the rock directly beneath it.
- [14]
The explosions damaged the already stressed rock and weakened the surrounding crust; stresses then gradually redistributed through the damaged rock, eventually causing nearby faults to slide years after the blasts stopped.
- [15]
"The Mt. Mantap sequence demonstrates that UNEs [underground nuclear explosions] can produce long-lasting crustal effects in a heterogeneous and critically stressed environment."
- [16]
"Repeated underground nuclear tests [have] progressively disturbed and damaged the surrounding rock and changed the stresses acting on pre-existing faults," says Kwang-Hee Kim, seismologist and geophysicist at South Korea's Pusan National University and a co-author of the study.
- [17]
Kim says the most recent nuclear test, in 2017, caused the most damage, and that after some seismic faults on the mountain were disturbed it started a domino effect.
- [18]
The 2017 test had an estimated yield equivalent to between 100 and 250 kilotons of TNT, up to 20 times as much energy as the blast that levelled Hiroshima in 1945.
- [19]
Paul Richards is a Columbia University seismologist who was not involved in the research.
- [20]
"The phenomena they've identified and documented is a bit surprising," says Paul Richards.
- [21]
Richards says the situation is "potentially dangerous": "Will it lead to even bigger earthquakes?"
- [22]
Mount Mantap is an archetypal "tired mountain", a Cold War term for a nuclear test site where the ground is so fractured by massive underground explosions that it becomes useless and can no longer trap radioactive gases from the blasts.
- [23]
The 2017 thermonuclear test effectively collapsed the top of Mount Mantap.
- [24]
The damage means there are no known plans to conduct future tests beneath the peak itself, but others may still be conducted at different underground sites at the Punggye-ri test complex surrounding the mountain.
- [25]
North Korea gives few details about the Punggye-ri complex, and the study is based mainly on data from seismographs in China and South Korea and satellite photographs of the terrain.
- [26]
The 955 located tremors are about 68 percent of the 1,399 detections, leaving 444 detected events without a mapped position.
- [27]
The continuous seismic record analysed begins in 2008, two years after the first test in 2006.
- [28]
The record covers about eight years after the 3 September 2017 test, and activity was still rising at the end of it.
Sources
2 independent publishers whose own reporting we read for this story.
- phys.orgNorth Korea's nuclear testing may have triggered hundreds of earthquakes over several years
1 article · September 18, 2026
- scientificamerican.comNorth Korea’s nuclear tests have turned this mountain into an earthquake hot spot
1 article · September 17, 2026
Topics and entities
Topics
- Induced Seismicity
- Nuclear test monitoring
- Underground nuclear testing
- Matched-filter detection
Entities
- North Korea
- Punggye-ri test complex
- Science
- Columbia University
- Chengdu University of Technology
- Pusan National University
- Comprehensive Nuclear-Test-Ban Treaty