Check out the linked picture made with Google Earth. I had made the place marks several weeks ago using information from blogs like ArmsControlWonk and DefenseTech. The mark with the long/lat coordinates is the location reported a few hours ago by the USGS. In particular, ArmsControlWonk posted information about the suspected test area that has turned out to be dead on.
Intelligence in the blog-o-sphere about DPRK nuke test was accurate