North Korea Set Off a Nuke Under a Mountain
By: Darren Orf
A 2017 nuclear test may have reactivated dormant faults under Mt. Mantap.
Here’s what you’ll learn when you read this story:
North Korea’s Punggye-ri nuclear test site is located at Mt. Mantap, in the reclusive nation’s rugged northeastern wilderness.
Even though it sits on stable intraplate crust, the area has experienced increased seismicity since 2017, when North Korea conducted its last and largest nuclear bomb test there.
A new study finds the blast’s stress redistribution reactivated two subparallel NNW-trending faults, confirming humans can wake dormant faults under the right geological conditions.
In the Hamgyong Mountains, located in northeastern North Korea, lies the relatively nondescript Mt. Mantap. At 7,234 feet tall, the mountain isn’t even the highest peak in its range (that distinction belongs to nearby Kwanmo Peak), but what unfolded beneath this modest mountain for more than a decade greatly concerned the entire world.
From 2006 until 2017, the Democratic People’s Republic of Korea (DPRK) conducted a series of underground nuclear tests at the Punggye-ri nuclear test site, just south of Mt. Mantap’s summit. While such tests are banned by the 1996 Comprehensive Nuclear Test Ban Treaty, the famously reclusive country (along with India and Pakistan) never signed it, so its nuclear weapons testing continued unabated.
On September 3, 2017, DPRK conducted its largest—and last—nuclear test at the site, with the U.S. Geological Survey recording the detonation as a magnitude 6.3 seismic event. Following this thermonuclear test, satellite images confirmed that the mountain shifted horizontally roughly 12 feet and sank by almost two feet.
Like other underground nuclear test sites throughout history, such as the Nevada National Security Site in the U.S. and the Semipalatinsk Test Site in Kazakhstan (then part of the Soviet Union), scientists expected the seismic rumblings that initially followed the test to fade in the ensuing days and weeks, as deformed crust relaxed to equilibrium. But that didn’t happen.
According to a new study published in the journal Science, Mt. Mantap has actually seen an increase in seismicity since the last thermonuclear test there nearly a decade ago. This region of North Korea, known as North Hamgyong Province, isn’t historically known for earthquakes due to its location on stable, intraplate continental crust, so scientists began exploring a troubling question: Did nuclear tests somehow reawaken fault lines in Earth’s crust?
“Unlike typical post-explosion sequences, which decay rapidly, seismicity at Mt. Mantap continued to increase for years after the final test,” the study authors write. “The progressive increase in both the earthquake rate and the moment release rate indicates that the crust did not simply relax toward equilibrium after the final explosion; rather, seismicity expanded gradually as preexisting faults became active.”
Studying the seismicity around Mt. Mantap—a nuclear test site within the most reclusive nation in the world—wasn’t easy, but the authors relied on data gathered in China and the Republic of Korea between 2008 and 2025. The study identified 1,400 seismic events within that time period and concluded that 955 of them occurred after the nuclear-induced earthquake in 2017. Researchers then plotted the hypocenters of each event geographically and discovered that most occurred along two subparallel NNW-trending faults.
One of these appears to extend a previously mapped fault south of the testing site, suggesting that structure has reactivated. The other branch follows no known fault line, but the scientists report that it displays “fault-like geometry.” Interestingly, these seismic rumblings increased in frequency years after the final nuclear test, meaning there was likely a delayed geological response to the explosion.
“According to this interpretation, the explosions altered the stress field and fracture network in the shallow crust, initiating a prolonged phase of structural adjustment,” the authors write. “Over time, stress redistribution gradually activated nearby faults, and the seismicity became organized into a broader fault network rather than remaining confined to localized damage zones.”
The study confirms that under certain geological conditions, humans have the destructive capability to reactivate fault lines, and in the near term, this increased seismicity might complicate methods for detecting further nuclear bomb testing in the region. While the world at large no longer conducts underground nuclear tests, Mt. Mantap serves as a warning that such future endeavors could have devastating seismic consequences.
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