Researchers from South Korea and China have documented a surprising rise in seismic activity surrounding the former Punggye‑ri nuclear test site in North Hamgyong Province. The study, published in Science on Thursday, analyzed data from 2008 through 2025 and identified 1,399 recorded quakes, most of them shallow events with magnitudes between 2.0 and 3.0.
Background on the test site
Between 2006 and 2017 North Korea conducted six underground nuclear explosions at the Mount Mantap complex, the last of which in 2017 produced an estimated 160‑kiloton yield and triggered a magnitude‑6.3 earthquake. The blast is believed to have caused a tunnel collapse at the site.
What the new data show
Lead author Kwang‑Hee Kim, a professor at Pusan National University, noted that seismicity was sparse before 2017 but began to climb sharply after the final test. Unlike typical post‑explosion tremors that fade within weeks, the region’s earthquake frequency has continued to rise in a clear, linear trend over the past several years.
“The Earth’s crust has a long memory,” said Sunyoung Park, an assistant professor of geophysical sciences at the University of Chicago, who was not involved in the research. “Short‑lived disturbances can have consequences that persist for years or even decades.”
Possible causes
The researchers suggest that the underground detonations may have re‑activated pre‑existing intraplate faults—ancient fractures far from active plate boundaries. Mount Mantap’s steep, asymmetric topography could have placed some faults closer to failure, allowing the explosions to act as a trigger.
Kim explained that water infiltrating newly created cracks can raise pore pressure, effectively pushing faults apart and making them easier to slip. Because water moves slowly, the resulting seismic response can be delayed by years.
Broader context
Human‑induced seismicity is not unique to North Korea. The Netherlands has experienced more than 1,700 earthquakes linked to gas extraction since the 1960s, and Oklahoma saw a marked increase in tremors from wastewater injection between 2009 and 2015.
While the observed quakes are modest and have not caused reported damage, the findings raise questions about long‑term monitoring of former nuclear test sites. Distinguishing between explosion‑related events and natural tectonic activity may become more challenging as the seismic record evolves.
What remains unknown
The study did not include data from North Korean monitoring stations, and the authors have no evidence of additional nuclear tests since 2017. International observers, including the International Atomic Energy Agency, have noted that North Korea began restoring test tunnels in 2022, and a 2025 U.S. Defense Intelligence Agency report confirmed ongoing restoration efforts.
Further research will be needed to determine whether the increased seismicity poses any risk to nearby communities or to regional stability.
Original reporting: KTVZ (Central Oregon) — read the source article.
