SEOUL (NYTIMES, AFP) - Analysts peering at satellite images of North Korea after the latest nuclear test reported on Tuesday (Sept 5) that they had spotted many landslides and wide disturbances at the country's test site, in the North's mountainous wilds.
Tunnels for the nuclear blasts are deep inside Mount Mantap, a mile-high peak.
The respected 38 North website, which is linked to Johns Hopkins University in the United States, published satellite images taken on Monday, one day after the nuclear detonation.
The images showed changes in the surface at the Punggye-ri test site where the ground had been lifted into the air by the tremors, and small landslides going into stream beds.
"These disturbances are more numerous and widespread than what we have seen from any of the five tests North Korea previously conducted," three experts wrote in an analysis for 38 North.
"There does not appear to be any evidence of a collapse crater, as might have been suggested from the post-test tremor," it added.
Early readings from global networks that monitor shock waves suggest that the nuclear blast on Sunday had a destructive power equal to 120,000 tons of high explosives. If correct, that is roughly six times more powerful than the North's test of September 2016, and eight times larger than the bomb dropped on Hiroshima in 1945.
Planet, a company in San Francisco that owns swarms of tiny satellites, reconnoitered the secretive nuclear test site. The three analysts - Frank Pabian, Joseph Bermudez Jr., and Jack Liu - said the wide disturbances appeared to include numerous landslides throughout the rugged site "and beyond".
They added that they could find no evidence of a surface crater that would have formed if the cavern carved out within the mountain by the blast's violence and high temperatures had suddenly collapsed.
The underground blast on Sunday caused a 6.3-magnitude earthquake, according to the US Geological Survey, and was followed a few minutes later by another with a magnitude of 4.1, leading to suggestions that the rock over the site had caved in, potentially releasing radioactive material into the atmosphere.
Pyongyang said the test was of an H-bomb that could be fitted onto a missile, heightening tensions over its weapons ambitions and prompting global condemnation.
Seoul's nuclear safety agency said on Wednesday it had not detected traces of radioactive materials, such as xenon gas, in soil, water and air samples following the blast.
Background radiation in South Korea appeared not to have been affected by the test, it added.