The temples ARE fortresses. Literally. It is a major attribute of their design. Those fences around them are not just for decoration.
I was able to tour the interior of the one in Bellevue Washington right after it was built. Those things are designed to withstand not only severe earthquakes, but also small wars and even relatively near nuke strikes.
They are actually quite impressive.
They are actually quite impressive.
Which brings up the question of just WHO would be allowed in those gates in the event of a catastrophe.
It may interest you to know that entrance to mormon temples is dictated by the issuance of a "temple recommend" and only the select members that obey all the mormon rules to the letter are given one.
I, for one, doubt the rules would be relaxed in the case of a civil emergency.