There have now been three detected and reported earthquake-like events subsequent to the most recent, very large (~6.1 magnitude) underground nuclear test conducted by North Korea on September 3, 2017 at its Punggye-ri Nuclear Test Site. Recent media reporting has suggested that, as a result, the site may no longer be suitable for further underground nuclear testing. The three earthquakes were likely induced by the ~250 kiloton nuclear test; however, US nuclear test history at the Nevada Test Site provides evidence that such post-test tremors are not unusual. Furthermore, even in the face of what has been dubbed "Tired Mountain Syndrome,"[1] abandonment of the site for nuclear testing should not be expected. Such historical precedent, combined with the presence of two other, as yet unused tunnel complexes within the test site, leads us to conclude that there is no valid reason to assume that the Punggye-ri test site is unable to contain additional underground nuclear tests.
As a result of these nuclear test-induced earthquakes, new media reporting has appeared with headlines such as "North Korea’s Nuclear Test Site Could Be Unstable" and "Has N. Korea nuked itself out of a nuclear test site?" 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." Nonetheless, based on the severity of the initial blast, the post-test tremors, and the extent of observable surface disturbances,[3] we have to assume that there must have been substantial damage to the existing tunnel network under Mt. Mantap. 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. A lack of new tunneling in this area would provide evidence that this mountain has been abandoned for future testing. However, complete abandonment of the test site as a whole remains unlikely.
At Punggye-ri, the presence of two other test tunnel complexes, accessible via the South and West Portals, provides sufficient means to continue testing at the site irrespective of test-induced effects to Mt. Mantap.