Bug out on foot? Not going to happen. It's too far to any kind of better shelter than what I have right here and both directions necessarily cross the major earthquake faults so the damage would increase.
It does depend on the scenario, though. I have a sister who lives on a farm about 120 miles away. I keep enough petrol on hand to drive there, but if for some reason that wasn't practical it could be an interesting journey to make on foot.