I don't think that the MOAB killed anyone.

[popeyespappy]

Waves can interfere constructively or destructively, and so, pressure would be greater at certain points than at others.  However, below ground (which was where ISIS was, supposedly), would not be effected very much, assuming, of course, that their tunnels were sufficiently deep, which was the whole point of my OP.

Yes waves can interfere with each other when they are out of phase. That's how active noise cancellation works. The effect can also be used in radar receivers to eliminate ground clutter. But that's not what is happening here. With the Mach Stem effect you essentially have a strong wave being pushed from behind by a faster wave.

No the MOAB isn't the best conventional weapon at our disposal for use against hardened targets or deep tunnels and caves. That would be the 30,000 lb. GBU-57A/B Massive Ordnance Penetrator (MOP). A penetrator type weapon designed to explode after contact once it is deep into the ground/bunker. The MOB has not been used in combat yet. That doesn't mean the MOAB wasn't effective against this target. The Afgan forces that investigated site reported that the bomb collapsed 3 tunnels/caves so apparently it worked.

ETA: Apparently the angle the incident wave meets the reflective wave determines how effective the Mach Stem effect is, but it is still an additive effect no matter how acute the angle is.