When a tsunami comes, the only answer is higher ground. The fact that there were strong multi-story buildings no doubt saved many. The only other help is early warning. While the Pacific Ocean had a fully capable warning system, the Indian Ocean did not, because Indian Ocean tsunamis are rare. Solutions for that problem have been and are in the works; a warning system, similar to that in the Pacific, is being built. Eventually, probably, a large earthquake in the Atlantic, like the Lisbon earthquake of 1755, will spur such a project there as well.
