I saw dozens of aquariums after the 94 Northridge quake. If you have a sizable tank there isn't much you can do.
I was inside a fish tank store with 5 rows of tanks. Some tanks were chucked across the aisle but 95% of them stayed in place. There wasn't any difference between glass or acrylic - if the tank got flung it got flung. But there was little rhyme nor reason why in a row of 20 tanks only 1 or 2 tanks went flying.
I saw 75g tanks that were braced to the wall, rip the studs right out of the wall and the tank bounced into the middle of the room tank still standing up and intact.
I saw several tanks that were strapped to the wall and the straps just ripped out of the stand or the studs in the wall. But the tank was still standing.
I saw 400g tanks that walked themselved across the room - but stayed upright and water tight. With the tank and stand not joined together by any means at all.
And I saw 40g tanks that burst with the stand still sitting in the same spot it always sat on the carpet.
You are trying to fight mother nature, and if mother nature wants to knock your tank down there isn't much you can do about it. Strap the tank to the stand, and mother nature will just topple both. Strap it to the wall and when the wall moves at a different speed than the tank it might yank the stand out from under the tank.
There are so many variables. Lil rumbers seldom unsettle a tank and with a big one, well you got more important issues to deal with than is your tank standing underneath the pile of rubble.
Get yourself a nice solid stand, put it on a nice solid floor. And hope for the best.
For what it's worth I have a 90g freshwater cube - not mounted to anything, a 750g not mounted to anything, a pair of 180g frag tanks not mounted to anything. And I live in Encino just a few miles South of the Northridge quake.
During the quake I had a 125g talll reef tank, and 1 rock tumbled from the top to the bottom. The room directly above the fish tank was my library - the books were thrown off the shelves and in a pile in the middle of the room. Tank didn't move a 1/4".
Dave B