I make sure that the tank cannot just slide off the top of the stand and secure the stand against the wall.
I have survived a few smaller quakes.
Against a bigger one, one has to brace the top of the tank with a frame or strip and secure against the wall.
Nothing would help if a very big one hits, IMO, but may be in a borderline case half of the water will spill and many livestock can still be saved.
Quakes do not move the ground all in the same way, I think. Even in a large quake, there can be more a swaying movement than strong jolts.