USGS just changed their heading to “NUCLEAR EXPLOSION”
M5.1 Nuclear Explosion - 21km ENE of Sungjibaegam, North Korea
2016-01-06 01:30:01 UTC 41.300N 129.047E 0.0 km depth
http://earthquake.usgs.gov/earthquakes/eventpage/us10004bnm#executive
Earlier today this was reported leaving air base in US:
https://twitter.com/USCitizen95/status/773966592644231169