North Korea's nuclear testing may have triggered hundreds of earthquakes over several years

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Between 2006 and 2017, North Korea conducted six underground nuclear tests at its vast testing site at Mount Mantap in North Hamgyong province. Typically, underground explosions trigger an intense burst of minor earthquakes that die down once testing stops.

But geologists have detected far more seismic activity after the final detonation, and it has persisted for years. The region was previously considered geologically quiet. No crustal earthquakes had been documented within 50 kilometers (31 miles) of the site for more than a century.

But all that changed in 2017. To discover exactly what was happening underground, an international research team led by Xingli Fan from Chengdu University of Technology analyzed 17 years of continuous seismic wave data recorded between 2008 and 2025. The data came from regional monitoring stations in China and South Korea, located 80 kilometers (50 miles) to 200 kilometers (124 miles) away.

They also used a sensitive pattern-matching technique called matched-filter detection to find smaller, hidden tremors that standard earthquake monitoring networks usually miss. Their findings, published in the journal Science, challenge long-held assumptions about how the Earth responds after an underground blast. Rather than fade away as expected, the seismic activity near Mount Mantap steadily increased and accelerated through 2025.

In total, the team detected 1,399 small local earthquakes. Mantap continued to increase for years after the final test," the study authors wrote. They also mapped the precise locations of 955 of these tremors and discovered they were not randomly located.

Instead, they lined up along two distinct, roughly parallel tracks stretching away from the test site. One of these tracks followed the projected continuation of a fault line geologists already knew about. The second track revealed what appeared to be a completely hidden fault that had never been mapped before.