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Scientists detected prolonged seismic activity at North Korea’s Punggye-ri nuclear test site years after its 2017 test, unlike typical post-explosion patterns.
News18
Scientists have detected an unexpected and prolonged increase in seismic activity around North Korea’s Punggye-ri nuclear test site, with the activity continuing for years after the country conducted its final and most powerful nuclear test in 2017, a CNN report mentioned.
The report mentioned that North Korea carried out six underground nuclear tests between 2006 and 2017 at the Punggye-ri site at Mount Mantap in North Hamgyong province.
The sixth and final test, estimated to have had an explosive yield of 160 kilotons, triggered a magnitude 6.3 earthquake and is believed to have caused a collapse at the site, possibly involving a tunnel.
Scientists have long known that underground nuclear explosions can trigger small earthquakes. Such seismic activity has also been observed around nuclear test sites in places including Nevada, where the United States conducted tests during the Cold War.
However, those earthquakes typically occurred within days or weeks of an explosion and were concentrated around the immediate vicinity of the test site.
The effects of nuclear testing at Punggye-ri appear to have been different, according to CNN. Kwang-Hee Kim, lead author of a study published Thursday in the journal Science, said the tests did not initially appear to have significantly affected the Earth’s crust. However, seismic data collected between 2008 and 2025 by Kim and colleagues in South Korea and China showed a sustained increase in earthquakes around Mount Mantap.
The researchers identified 1,399 earthquakes in the area during the period covered by their analysis, with both the frequency and magnitude of the seismic events increasing over time.
“The broader lesson is that short-lived disturbances can have consequences that persist for years or even decades,” Sunyoung Park, an assistant professor in the University of Chicago’s department of geophysical sciences who was not involved in the study, said. “The Earth’s crust has a long memory.”
Seismic Activity Rose After 2017 Test
The first earthquake identified by the researchers occurred in 2013, following North Korea’s third nuclear test. However, seismic activity around Mount Mantap remained relatively sparse until 2017.
According to the study’s authors, seismicity increased markedly after North Korea conducted its sixth and largest nuclear detonation in September 2017. Unlike the usual pattern seen after underground explosions, however, the earthquakes did not gradually subside. Instead, seismic activity continued to rise for years after the test.
“We were basically very shocked,” Kim, a professor in Pusan National University’s department of geological sciences in South Korea, said. “The seismic trend was so clear and linear.”
The earthquakes detected in the region were generally small, with most measuring between magnitude 2 and 3. Kim said the events also appeared to have occurred at relatively shallow depths.
Why The Findings Matter
The Mount Mantap region was considered seismically quiet before the nuclear tests began. The study noted that earthquakes in the area had been “virtually unknown” before this century.
Kim said historical records spanning more than 2,000 years in China and Korea contain very little evidence of significant seismic activity near the site. He noted that researchers found one historical event roughly 100 kilometres away, but said the region’s overall seismic activity had been very low.
The Korean Peninsula also differs from highly active earthquake zones such as Japan. It sits on relatively stable continental crust rather than directly on an active tectonic plate boundary.
However, researchers identified ancient fractures known as intraplate faults beneath the region. These are pre-existing faults located within a tectonic plate, rather than along its boundaries.
The scientists suspect that the nuclear explosions may have acted as a trigger for some of these previously inactive faults. Kim said the increasing rate and intensity of earthquakes suggest that the Earth’s crust around Mount Mantap may not have returned to its pre-test state after the 2017 explosion.
Instead, at least two pre-existing faults may have become active, according to the researchers.
Quick Answers
Ask News18The 2017 nuclear test, which was North Korea’s sixth and most powerful detonation, triggered a marked and sustained increase in seismic activity around Mount Mantap. Unlike typical post-explosion earthquakes that subside within days or weeks, the seismic activity at Punggye-ri continued to rise for years after the test. Researchers identified 1,399 earthquakes in the area between 2008 and 2025, with both the frequency and magnitude of these events increasing over time.
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Covering day-to-day national and international news for the last nine years across print and digital. Associated with News18.com as Chief Sub-Editor since 2022, covering innumerable big and small even…Read More
September 18, 2026, 09:28 IST
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