I tried to apply the formula in Pell's case so to see what kind of result i get.
For the distance i decide to use 1 meter, as i didn't want to use pixerscale and i wanted to find an acceptable bare minimum.
Even if i would like to remind that the scans
show that Pell was much closer than 1 meter when the explosion happen.
Bomb = 355.890124 Kilotons or 355890.124 Tons
Distance = 1 m
CA = 0.83 m^2
(355890.124/(4π(1)^2))*0.83 = 23506.2941 Tons of TNT or 23.506 Kilotons =
Town level
Even with the Inverse Square Law, Pell's its still around Tier 7.