[gerdesj]

That may or may not be true but as per the article, building standards like that are defined in terms of 1 in 100 or 1 in 1000 year events etc. The years bit in Japan will be defined already in their standard for designing a protection for tsunami events. Now, I don't know what 1 in n years is used but I suspect that it would be 1 in 500 or 1000 years. If a 1 in 10000 years event turns up then the inevitable happens.

So all we have to look up is the standard and the event and compare. Even then you have to design to account for what to do and what happens in the event of your wall's failure and that is probably where things went really wrong.

You could always read things like this: https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1710-Repor...