Study finds more than 1,300 earthquakes near Punggye-ri since the North’s sixth and most powerful nuclear test in 2017
North Korea’s underground nuclear tests may have reactivated long-dormant faults beneath the Punggye-ri test site, causing more than 1,300 earthquakes in the area since 2017, according to a study published in Science on Thursday.
An international research team led by Pusan National University geological sciences Professor Kim Kwang-hee made the finding after analyzing 17 years of continuous seismic waveform data collected in South Korea and northeastern China between 2008 and May last year. The team included researchers from four Chinese institutions: Chengdu University of Technology, the Chinese Academy of Sciences, the China Earthquake Administration and Shandong University.
In the study, titled “Nuclear tests at Mt. Mantap have reactivated intraplate faults,” the researchers tracked changes in seismic activity around Mantapsan in Kilju, North Hamgyong Province, where the North conducted all six of its nuclear tests.
The study found no recorded earthquakes in the area before North Korea’s first nuclear test in 2006. About 60 quakes were detected between then and the country’s sixth and most powerful test in September 2017, with seismic activity gradually increasing after the third test in 2013.
That pattern shifted dramatically after the 2017 test.
Seismic activity intensified about 20 days after the detonation and has continued ever since, with researchers detecting roughly 1,330 earthquakes. Most occurred along two fault zones that extend for about 24 kilometers in a north-northwesterly direction.
The earthquakes also grew stronger over time. Their magnitudes initially ranged from 1.0 to 1.3 but reached the magnitude-3 range in 2023 and 2024. The strongest registered a magnitude of 3.4.
The researchers said the repeated nuclear explosions likely fractured and weakened the shallow crust beneath Mantapsan. The blasts may also have placed additional pressure on the surrounding rock, gradually reactivating faults that had long been dormant.
Most earthquakes on the Korean Peninsula occur at depths of about 15 kilometers. But most of those detected near the North Korean mountain originated less than 1 km below the surface, suggesting that they were linked to the underground nuclear tests.
Professor Kim said the 24 km fault system could produce an earthquake of up to magnitude 6.4 if the entire system were reactivated at once.
“The seismic activity did not quickly subside after the 2017 nuclear test,” Kim said. “The earthquakes continued for years and gradually formed a clearer pattern along existing faults.”
The findings challenge the assumption that seismic disturbances from underground nuclear explosions fade soon after a test. The researchers said the impact can persist for years, depending on the area’s geological conditions and the pressure already affecting nearby faults.
The study could affect efforts to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty. The researchers said monitoring should continue long after a suspected nuclear explosion because earthquakes linked to the blast may persist for years.
junheee@heraldcorp.com
