The earthquake caused by the 2016 nuclear test was 5.1 magnitude,[2][14] similar to the 5.1-magnitude earthquake that accompanied North Korea's previous 2013 nuclear test (which was estimated by South Korea to have a yield of 6–9 kilotons of TNT and Russian estimates of more than 7 kilotons of TNT).[15][16] https://en.wikipedia.org/wiki/2016_North_Korean_nuclear_test So if the 5.6 reading the USGS calculated stands, the yield should be well over 10 kilotons?
5.6 equates to kilotons of energy per UCLA.
http://www.english.ucla.edu/all-faculty/335-kelly-kiloton-index-of-earthquake-moment-magnitudes
Not necessarily an actual yield though , I guess.