NHK reports, as investigations continue into the tsunami... one town was hit with 19.9m (52') waves. Now, that just seems unfair in some way. (Yes, I know that's a bit silly to say, but it's the way I feel.)

The footage of these investigations is humbling and also fascinating from an engieering point of view. The failure modes for a number of large buildings "well designed" for tsunamis was surprising to me at first glance. They fell toward the ocean. Most which withstood (stayed vertical although obviously sustaining major damage) the initial forces were toppled by the receding waters indicating that these buildings could structurally withstand cyclical impact loading of short duration but were susceptible to the following continuous loads in the opposite direction. Yes, there certaily would be a weakening factor due to loads but, empirically, I just wouldn't have clued into that failure mode if I had not seen the videos.

That's a very short and skimpy description which leaves out many variables... pathways of receding waters concentrated by drainage contours, debris concentration in similar fashion... many other considerations.