guys, the icbms are a fallout fact, the emperor stated that the sub had lost power after firing the missiles... If I remeber corectly (course it is FT2)
as for west tech, I seem to recal the area was saturated with nukes, though how the crater was created... dunno, it might depend on the tipe of weapon we aretalking about, or hell, maybe a defect on the armoring structure, but it seems it was vaporized in a perfect sphere...
perhaps it was a weird ass experimental weapon that broke the plate at west tech... plasma?