No, I want to increase my chances of getting stuck inside of a chunk of the Earth in the event that it explodes; I need it to be buried as deeply as humanly possible; the maximum depth depends on how much weight it can withstand lol.
An impact strong enough to split the Earth in two will likely destroy everything on the surface, and likely a good distance below the surface as well. So yeah, I want my bunker to be SUPER deep lol.
Then when my half of the Earth is being ripped apart by all the gravitational forces at play, my bunker will effectively become a spaceship so long as it has it's own oxygen supply and reinforced exterior. All I'd need is a means of propulsion and a safe-ish way to crash-land it on the nearest inhabited planet. In our case, that would be Mars, in the event the aliens haven't already blown it to smithereens in anticipation of a few humans managing to escape Earth's destruction. Hopefully at that point, we'll already have bases set up on Mars. If not, then I guess we'd be the First Human Colony of Mars, which would like, REALLY suck lol.