ABSTRACT

Satellite‐based Synthetic Aperture Radar (SAR) data of the Punggye‐ri nuclear test site, along with pre‐ and post‐test optical commercial satellite imagery and a short official video (which was apparently recorded during the 3 September 2017 test), provide additional insights on the widespread surface disturbances around the peak of Mt. Mantap. These were generated by North Korea’s sixth and by far largest nuclear test (estimated to be roughly a quarter of a megaton; Zerbo, 2017). Although a number of visible landslides that are associated with this test had been previously reported, these additional data reveal more information about the widespread nature of the detected larger‐scale movements that have been reported by other researchers, in addition to some smaller scale instances of localized slumping or compression within the top 200 m of the mountain; these took place in an area that was observed to contain stratified volcanic deposits not otherwise described to date. A closer look at two previously described zones of localized slippage, subsidence, or slumping (located within those identified volcanic layer deposits on the western side of Mt. Mantap) revealed useful information about the landscape of the area. Several healthy trees have been knocked down in one zone; in the other, a rock prominence had collapsed, and a 60‐m‐long crack or crevice appeared to have opened. It remains unclear whether these surface disturbances were associated with what had been allegedly reported by the news media as a “cave‐in that was externally observable.” However, given the likely 800 m depth of the test in the lower hard‐rock geology, we have been led to conclude that the notable observed localized surface disturbances cannot be interpreted as a “collapse crater” that was a result of a “cave‐in” above any nuclear test created cavity and/or associated tunneling. Although the broadscale nature of the SAR and visually detected movements inhibits more precise geolocation of the test within the mountain, the radar imagery did show that the various surface ground movements were generated in opposing directions. The movements were directed away from the center on either side of the mountain; as such, they provided an empirical basis to confirm the previous seismological estimates that the detonation had occurred somewhere under the peak of Mt. Mantap. Moreover, a North Korean‐sourced short video that was acquired with a ground‐based camera focused directly on the peak shows a large dust cloud rising up from the mountain. This provides additional evidence that is consistent with that conclusion.

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