Satellite images suggest that North Korea’s sixth nuclear test caused several landslides at the secretive state’s mountainous test site, according to a U.S.-based watchdog.
The latest test was said to have been a hydrogen bomb designed to be mounted on a newly developed intercontinental ballistic missile that has “great destructive power,” state media said Sunday.
North Korea’s announcement came just hours after a large earthquake was detected near the country’s only known nuclear test site in the mountainous region of North Hamgyong province.
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According to U.S.-based North Korean watchdog 38 North, satellite images suggest the nuke test resulted in landslides occurring at the Punggye-ri test site.
“These disturbances are more numerous and widespread than what we have seen from any of the five tests North Korea previously conducted,” the watchdog noted in a blog post. “There does not appear to be any evidence of a collapse crater, as might have been suggested from the post-test tremor.”
The U.S. Geological Survey (USGS) recorded a seismic event measuring 6.3 in magnitude Sunday near the Punggye-ri test site. A smaller 4.1 magnitude event was recorded about eight and half minutes later, suggesting a structural collapse of sorts.
“Among the possibilities for such an event the USGS proffered that it was a post-test ‘tunnel collapse,’ but it could also have been a ‘chimney collapse,’ caused by the area above the test cavity collapsing downward forming an upward shifting cavity known as a chimney,” 38 North previously noted.
The smaller event could have been a “landslide or other earth movement induced by the large test.” The watchdog added that “such a post-test event of this magnitude increases the likelihood” of the release of radiation.
According to Reuters news agency, China’s Nuclear Safety Administration said on Monday no radioactive particles were detected along its border with North Korea.
Earlier this week, a Chinese scientist warned North Korea’s test site may be at risk of collapsing, releasing “many bad things.”
Speaking with the South China Morning Post, Wang Naiyan of the China Institute of Atomic Energy said if such a collapse should happen, it would pose a radiation threat to both North Korea and regions of bordering China.
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“We call it ‘taking the roof off,'” Naiyan told the newspaper. “If the mountain collapses and the hole is exposed, it will let out many bad things.”
Naiyan told the paper that because of North Korea’s limited land area, the country doesn’t have many options for hosting a nuclear test site. Depending on how and where the bombs are placed within the mountain may determine how much longer it can hold up to another test.
“If the bombs were planted at the bottom of vertically drilled tunnels, the explosion would do less damage,” Naiyan told the newspaper.
Naiyan noted that vertical tunnels were more expensive and difficult to build, so boring horizontal tunnels into the mountain would be easier but increases the risk of blowing off the mountain top.
“A 100 kiloton bomb is a relatively large bomb. The North Korean government should stop the tests as they pose a huge threat not only to North Korea but to other countries, especially China,” Naiyan told the newspaper.
It’s unclear the size of the bomb North Korea detonated Sunday. According to Japan’s defense minister, the test could have been in the range of a 70-kiloton bomb.
— With a file from the Associated Press.