Analysts keeping an eye on North Korea say “substantial damage” to its nuclear test site could force Pyongyang to abandon the underground complex of tunnels where it has conducted most of its test blasts, and move into other areas.

That assessment—published on Tuesday by the watchdog 38 North, part of the U.S.-Korea Institute at Johns Hopkins SAIS—is based on the severity of North Korea’s sixth (and largest) underground test on September 3, post-blast tremors and observable surface disturbances on Mount Mantap.

North Korea has conducted five of its last six nuclear tests in a complex of underground tunnels accessible via a portal.

“If North Korea were to attempt to continue testing under this mountain (such as in the area more to the eastern side), then we would expect to see new tunneling in the future near the North Portal, still under Mt. Mantap,” states the 38 North report by Frank Pabian and Jack Liu.

“A lack of new tunneling in this area would provide evidence that this mountain has been abandoned for future testing,” the report states. “However, complete abandonment of the test site as a whole remains unlikely.”





The analysts released the assessment to address media reports that North Korea appeared to have nuked itself out of its Punggye-ri test site, and that the area could be unstable.

Kim So-gu, head researcher at the Korea Seismological Institute, told Reuters last week that the September 3 explosion was so powerful that the underground tunnels may have caved in. A 4.6-magnitude earthquake was detected at the site eight minutes after the detonation.

"I think the Punggye-ri region is now pretty saturated,” he said. “If it goes ahead with another test in this area, it could risk radioactive pollution."

The 38 North report states: “While these do make for eye-catching headlines, there was little substance in the articles to back them up beyond quoting the speculative fears of ‘civilian experts.’”

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Even in the face of “tired mountain syndrome”—alterations to the rock mass due to multiple nuclear detonations—abandonment of Mount Mantap “should not be expected,” the report states.

The tunnels through the north portal may no longer be in usable condition, but two yet-to-be-used tunnel complexes accessible via south and west portals exist at the site. That means Pyongyang would not have to build new tunnels to continue testing.

“For the time being,” the report concludes, “given the presence of additional test portals, we see no reason that the Punggye-ri Nuclear Test Site as a whole has or will be abandoned for future underground nuclear testing.”

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