according to cannon shields actually fail against em weapons, like the kayser or the banshee. with that little piece of data i dont see why emp blasts of nuclear weapons dont completely destroy shields. or perhaps the em of nukles are far less precisely tuned to result in shield damage while em weapons are. none the less if your at ground zero of a nuke blast your gonna hurt.
does anyone know what part of the em spectrom would mater/antimatter detonation generate. perhaps the gtva has the technology to precisely tune there weapons of mass destruction fully to the infrared spectrum thus causing more thermal damage.