There are furniture anchors that can be use. They consist of a piece plastic or wood connected to a cord, and another piece of plastic or wood. You can use one or two on your tank stand. The piece of plastic/wood would go inside the stand, you then drill a hole through the wood stand and run the cord out. The opposite end would be placed inside the wall to the rear of the stand. They can't be used on the tank, but if you use one on the stand, and then set up a similar thing for the tank using industrial velcro (available at Home Depot) you can "jerry rig" a similar design for the tank itself. I think this would work well on a 5.0 quake, but having been on the 27th floor of a building for the '89 Loma Prieta 7.1 quake, I don't think there is much that can be done to protect your tank from a serious quake.