We haven't done ANY nuke tests for a generation. Those could be the remains of old nuke blasts, but they are pretty small, and more likely they are conventional blasts. The largest hole is a few hundred feet across, and could be a nuke.
EDIT: They are nuke craters
"Along the way down that road, notice how there is absolutely no wildlife other than grasshoppers, that the Joshua trees suddenly turn to an enormous size and monstrous shape, and that the few cattle grazing around don't seem like any cattle you've seen before. Then notice those blasted-out craters in the earth, with the core sample holes in the center. When you realize you are looking at nuclear test sites, the desolation and mutations suddenly make sense. Wave hi at the guys in the military vehicles who are making damn sure you don't go through that gate, and hightail it out of there."
http://travel.latimes.com/dest...encounter-with-area-51