>>507764851Earthquake Bomb
It might also just possibly have a nuclear warhead which wouldn't produce a flash or radiation from the blast. A yield equivalent to 500 or 1000 tons of explosive. You can get away with that sort of thing.
Especially since a former spec ops guy just gave an interview saying it was definitely doable and only takes 2 hits (the first weakens the rock and damages some systems in the bunker)