I could see elephants being able to notice slight low sounds, from your numbers especially between 16 and 64 Hz, that humans might not notice. But, instead of sound, it is perhaps vibration. I may be mixing this up with something else, but did I see some animal show where elephants communicate over large distances (several km?) by stomping their feet? (I may be completely wrong here). So, it would not IMHO be impossible for elephants on Sri Lanka (are there elephants on SRI Lanka?) or Thailand to feel the mainshock while humans did not. Or, is it possible that the withdrawal of water along the coast just in advance of tsunami might set off some slight vibration (or, more likely, the tsunami striking somewhere down the coast). This is all speculation on my part, and your (John's) request that someone actually link to solid evidence for the existence of animals getting out of the way is well-taken...
Chris