Earlier this month, North Korea announced the closure of its nuclear testing site, saying it’s suspending all nuclear and intercontinental ballistic missile tests. The surprise move by President Kim Jong Un may be an attempt to ease relations prior to a summit with Donald Trump, but a new reports suggests the collapse of North Korea’s test facility may have been a contributing factor.
Geologists at the University of Science and Technology of China have presented evidence suggesting the mountain directly above North Korea’s Punggye-ri nuclear test site has collapsed, reports the Associated Press. The incident happened following the September 3, 2017 detonation of a nuclear bomb estimated at around 100 kilotons, which is 10 times stronger than any of the previous five tests conducted by North Korea. By comparison, the bomb used at Hiroshima in 1945 produced about 15 kilotons of explosive power.
The underground explosion generated four earthquakes in the weeks that followed the September test, triggering the suspected cave in. The first of these four earthquakes—registered as a magnitude 6.3—happened about eight minutes after the explosion, producing “an onsite collapse toward the nuclear test center,” according to the geologists. The subsequent quakes were recorded nearby within the 7,200-foot-high mountain.
These findings are consistent with a related study published in Geophysical Research Letters on March 14, 2018. “According to our model, the explosion created a cavity and a damaged ‘chimney’ of rocks above it,” wrote the researchers, who work at China’s Institute of Geophysics in Beijing. The analysis produced by the University of Science and Technology researchers has successfully gone through peer review, and will appear in an upcoming issue of Geophysical Research Letters.
To date, no radioactive materials have been collected along North Korea’s border with China, the AP reports, but Chinese officials aren’t taking any chances. There’s fear that radioactive dust may have seeped through cracks and holes in the damaged mountain. “In view of the research finding that the North Korea nuclear test site at Mantapsan has collapsed, it is necessary to continue to monitor any leakage of radioactive materials that may have been caused by the collapse,” explained the geologists in a release published earlier this week.
The announcement that North Korea’s nuclear tests are coming to a halt—at least for now—will likely come as a relief to Beijing. The mountain-based facility is located less than 60 miles (100 km) from Chinese border, and prior tests have triggered measureable seismic events, resulting in the evacuations of Chinese schools and workplaces.