This isn't my field, however, it seems a fairly straight-forward way to produce yet another body of evidence that could be easily verified independently. Although I have no access to the equipment necessary for this type of analysis, I am certain that the particles of crushed concrete will look categorically different from particles that have been in close proximity to highly energetic bursts. Those which have been exposed to explosions will have characteristic fractures that simple compression cannot produce.
Also, crushed concrete of a known variety will produce known amounts of particles of particular sizes--even when dropped 1400 feet. Particles smaller than this are automatically indicative of more energetic reactions. Thermodynamics cannot be fooled by propaganda.
Am I late to the game? Has this already been done?
EDIT: I've been corrected about that "certainty" thing.
Being pointed in a few directions…