No matter what area you are in, you naturally assume the worst can happen. Even if you think your area is relativly safe, reinforce your survival shelter for any circumstances, even high water. I had the thought that a dome with an attached, reinforced floor - so that essentially the shelter was all one piece - would not only survive dislodgement in an earthquake, but might also float. I think I read somewhere that during WWII they made some ships/boats out of concrete. If concrete will float, why not a one piece dome shelter? For instance, is the dome is shifted by a quake, right off its foundation, or heavy rain caused flash flooding and mudslides, which might shift it. If the dome was one continuous unit, walls and floor, it could be built strong enough to withstand a "slide" or shift from its original location, and remain intact and usable for the survivors. I'm just not sure of the feasability from an engineering stand point.
Offered by Brent.
I think a dome would have a tendency to tumble in the waves. So - one would need to tie securely everything down including bodies. If the dome had a weighted bottom, thicker on the bottom or heavy objects secured to the floor, then I think it would ultimately end up right-side up. It would have to be made with water proof doors or escape hatches. If anything like flying trees or boulders crashed into the dome and water leaked in - allow a battery operated bilge pump to turn on due to sensing the presence of water. You would need a way to get air in and out without water getting in. The idea has some engineering challenges, but is not beyond the range of possibility.
Offered by Mike.
Even though a floatable structure may sound like it's covering the contingencies, please consider that such an object is mobile and subject to the unpredictable action of waves and currents which will be severe at the time of the shift. Who knows what you might find yourself thrown against. It may be better to try to find an area far enough away from water and high enough to keep you dry if there is an unforseen incursion.
Offered by Richard.