Tsunamis are exceedingly hard to predict.
Warnings after a colossal 8.8 eatrhquake under the ocean are legitimate.
Except that, as another Freeper pointed out (I forget who) that when Easter Island only gets a negligable wave, it is completely irresponsible to panic the entire pacific Basin with warning about "fingers" of high waves radiating outward, since no such "fingers" have ever been observed nor reported, and wave energy decreases with distance.