After the 94 Northiridge Earthquake I got the chance to see dozens of tanks that were affected by the earthquake. There were no cracked tanks. There were tanks that toppled. But the biggest thing was seeing tanks all in one piece and standing moved to the middle of the room. There were tanks that had been strapped to the studs in the wall, and the tank bouncing ripped the studs out of the wall.
I saw a 125g tank sitting in the middle of the room with the section of the wall it was attached to, still attached to it in the middle of the room.
Having a bigger tank doesn't really make a difference, The weight of the tank is nothing in comparison to the strength of the earth bouncing underneath it.
When the earth starts to roll, your tank is going to roll with it. With a small tank you may be able to affix it to a wall. But with a larger tank, you get 1000lbs of water moving, it's going to keep moving.
Dave B