a couple of questions, did the tank previously have a center brace? and if so was the center brace cut or broken out? if these happen to be the case i would suggest building a a custom tank lid for it something that you can fit snuggly over the top of the tank, doing this will cut down the risk of explosion, when you build the lid for the tank make sure that you use quality lumber and water proof it! also when you build the lid make sure it covers the strip around the top of the tank, and use wood screws and wood glue so that your joints do not stretch, this will ensure that the tank remains stable, however this is something that i would take my time considering the amount of damage and the possible personal injury that a tank collapse could do in a home and to you or any of your family members. honestly i don't know how much you paid for the tank, and i don't know if you have any urge to keep lizards or any other type of animals besides fish, a 100 gal tank would make a GREAT terrarium for something like an iguana or other lizards or even a small python.......
good luck and think safety first!

Brandon