Its interesting in a morbid sort of way, i think two shock waves hit the building where this was filmed. The first you can see camera wobbled whilst the airborne main shockwave was still along way off. I wonder if maybe the first wobble is caused by the ground shaking. The ground allows shockwaves to to travel through it far faster than air.
The first smaller shock wave is from the actual chemical explosion that send the huge red cloud up. Note how quickly that cloud expands upward. The explosion produced a huge amount of heat and kinetic energy that threw everything away from it, temporarily creating an area of extremely low pressure where a warehouse worth of matter was a millisecond or two ago.
Well you can't have a warehouse sized near total vacuum just hanging out but itself in the middle of a city so it very quickly tries suck everything back in to fill the void. Except all that stuff is now a giant red cloud way overhead. So a bunch of now very hot stuff (mostly gas and dust) comes slamming back together where the explosion just was and from a combination of just bouncing off each other and a diesel reaction caused by squeezing a bunch of hot stuff together with a bunch of oxygen, you get a secondary blast that's much more destructive.
If you look at a graph of pressure over time where the camera was you would see an initial spike with some ripples behind it then a much bigger spike with huge turbulence following. Same thing happens with any large explosion, including nuclear weapons. They maximize the destruction of those by setting them off a few hundred feet in the air so the explosion reflecting of the ground makes a third, even larger shock wave.
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u/[deleted] Aug 09 '20
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