One of the lessons learned (In Japan at least) is that, while we can model sea barriers for waves “X” so high, we should also add very comfortable cushions into those estimates of wave height based on the land sinking.
The elevation of the land itself in the northeast part of Japan fell by about a meter in some places. This allowed the sea to overtop sea walls that were designed to withstand the wave height that they indeed saw.
If you told engineers 30 years ago that the entire chunk of land on which you’re now standing could go *down* by a meter (or more) in five minutes, they’d blink, look at you and say “Uh, really? Are you smoking something?” because we had no direct experience with this. Only since the advent of highly accurate three dimensional positioning systems (eg, GPS) from a reference point off the surface of the earth would we discover that a huge area of land just dropped, relative to the sea surface.
Yes. Look at our own Pacific North West, or for that matter how much the coastline changed after the 1964 Good Friday Alaska quake.
Come to think of it, 1964 was more than 30 years ago...