[jcims]

A 1 kg block of plutonium 12,000km away has ~5 orders of magnitude stronger gravitational field than a solar mass at 1 billion light years.

Presumably a sudden mass-energy conversion of said kilogram would generate a sharp gravitational wave. Assuming someone went back through LIGOs algorithms to fine tune them for such a detection, doesn't it seem plausible that it would be able to do so? And presumably even locate it?

[jcims]

I’ll toss out a guess that the signal is there but it’s so short that there isn’t enough to correlate across locations. So you might not be able to detect a detonation with it, but given a window of seconds from seismograph data you might be able to pinpoint location and corroborate yield.

[scentoni]

Only a small percentage of the plutonium's mass gets converted to energy during fission.

[jcims]

Indeed, this site says it's about 46g per megaton: http://www.jick.net/hr/skept/EMC2/node4.html

Still, 1kg has a field strength that's 5 orders of magnitude greater than a solar mass a billion light years away...10mg would be in the neighborhood.

If i didn't screw up the math, that's ridiculous.