OK, taking the report with a huge grain of salt, what size nuke would create quakes of the magnitudes reported? I’m thinking these would be extremely sophisticated tests, perhaps of the complexity only possible with outside technical assistance. If so, then we won’t hear boo about it since we’d not want to face the fact that China and / or Russia had a hand in it.
To get a 4.8 scale signal from a nuke test, it would have to be a large device, in excess of 1 MT - which I doubt they have. There’s quite a difference in complexity between a implosion or gun type fission device and a multi-stage thermonuclear device.
This is footage of the Cannikin Test, which gave a signal of about 6, and it was a 5 MT device 5000 feet down.
http://www.youtube.com/watch?v=qp6aZIhHiRE