Car = 142 px = 3 m
crater diameter = 810 px = 17.1 m
radius = a = 8.55 m
Since Graviton was able to stand inside it
h ~ 1.8 m (possibly a bit more but the result will still be the same)
Volume of spherical cap = πh/6 *(3a^2 + h^2)
V = 209.7 m^3
Under a few cm of concrete there is regular rock so i'll be using the value for regular fragmentation of rock (8 j/cc)
E = 1258200000 Joules (300 kg TNT) Building level