You can't really 'earthquake proof' but you can certainly 'make life easier/safer in case of an earthquake'. We had two large earthquakes several weeks apart (6.5 and 6.6). We live about 100km or so away from the epicentres so luckily we didn't get the full force.
Earthquake one: lost water out of the tank and power on the circuit as the water went up and over and down the wall and into the plug. It also fell onto my laptop which fried itself immediately. We cleaned up and put an extension cord on the power heads and one light. Got the plug replaced a few days later and away we went.
Earthquake two: lost water again but also lost power to the whole town for about 3 or 4 hours. Had a vortech set up so I got a little bit of circulation. FYI a small amount of water can travel great distances on a concrete floor ;-)
Here's what I have set up now:
water resistant 'raincoat' for the wall plug
taped power board to stand so it doesn't move and fall into water
zip tied power board to underside of tank stand
put all random leads/plugs into a box to keep it off the floor - has a lid to stop water splashing in
moved other electrical stuff around the corner
So basically keep heaps of old towels on hand (which if you have a fish tank you probably already have these), keep electrical stuff off the floor, stop stuff from moving (tape them down), have a plan if you loose power, get a tank with a lid.... And number one rule: DON'T go and stand next to your tank thinking you can hold it up to stop the shaking - you are precious and nothing is worth risking your life. Drop, cover, hold :spinner: