The calc here takes into account the power of the explosion and while that's okay, there's an overlooked part of the feat: the building destruction. The Buggy Bomb basically destroys everything on its path until it explodes, leveling part of the town in the process.
Following the same values from the previous calc, we get 52.98m tall buildings. Sadly we can't get good visuals of the buildings so I'll go with 40m as length and 26.49m as width for these rectangles as that's more or less the proportion shown.
Volume: 56137.608m^3 * 1000000 * 0.2 (to account the 80% of hollowness).
Volume: 11227521600 cm^3.
Jasonsith commented that this might be better if I add the results for concrete and pine wood.
Red Pine Wood's frag value is 4.1369j/cc.
Energy: 11227521600 * 3.0337 = 46447134107 joules.
Concrete's frag value is 6j/cc.
Energy: 11227521600 * 6 = 67365129600 joules.
Rock frag: 8j/cc.
Energy: 11227521600 * 8 = 89820172800 joules.
We see 6 buildings being destroyed by the Buggy Bomb so that result is multiplied by 6.
- Low End: 278682804642 joules or 66.61 Tons City Block level+ 8-B+.
- Mid End: 404190777600 joules or 96.6 Tons City Block level+ 8-B+
- High End: 538921036800 joules or 128.8 Tons Multi-City Block level 8-A.