I was thinking about Jones and his 9/11 video the other day.
In the video, he reported that there were two explosions in the OKC bombing. Both eyewitnesses and seismic sensors at universities detected two discrete explosions.
Anyway, I have an explanation:
McVeigh used commercial water gel explosives as boosters to detonate the main ANFO charges. I've set off bombs as a kid that had a combination of slow-burning and fast burning explosives (i.e., black powder, and flash powder) and you could distinctly hear the two compounds exploding, even though they were mixed together in the same package.
I think that's why witnesses at OKC bombing heard two explosions, and that the faster initiator charge registered seperately from the main ANFO charge. I'll have to watch his 9/11 video again, see the graph paper.
(Jones theorizes that the ATF planted high powered military explosives in the basement to coincide with McVeigh's crude homemade bomb, in order to spark a polic-state crackdown on militia and anti-government groups. I think that's insane).