I cant remember it's name but it lies very near the Chinese NK border and is quite far from any plate boundaries. There i was activity like 10-15 years ago or something. I remember it because there was a joint research effort between several countries which included us and NK...at NK request if i remember correctly.
I am doubtful these underground tests will affect anyone beyond the earthquakes.
From older studies with the US tests IIRC you need enough energy to produce earthquakes of around magnitude 9+ to have significant impact outside of a very localised area. To put it into perspective it took going from something like ~1Mt to ~5-6Mt to go from a 6.5 quake to a 7 quake so you'd need to be setting off underground devices in excess of 100Mt to get there :s