The only reason for god to punish them, that I can think of: Overpopulation, clearing some room for more people. I think the earthquake will make the island a little bigger (remembering a discovery made by Darwin, i think. i read in biology) and their will be less people to take up room. Don't want to be rude by saying this, but if you want a reason for god to do this, that's it. Or maybe he wasn't paying attention and wasn't able to stop or minimize it in time. Some things go on without him noticing, which can cause them to go out of control.