Engineering for the 1000 Year event:

The Japan Times Online today reports that "Signs of disaster were there to see"  There aren't many times that I feel like I live in the New World, but the article made me feel it:

The area devastated by the tsunami was hit by similar or even bigger waves when what is known as the Jogan earthquake occurred on July 13, 869.

Details recorded in some history texts, including "Nihon Sandai Jitsuroku" compiled in 901, suggest the seismic thrust was in the neighborhood of magnitude 8.6. Geologists have found sand deposits caused by the tsunami a couple of kilometers inland, meaning the quake was accompanied by massive killer waves as well.

That's some historical record!    

From an engineering perspective, this isn't the first time designing for an event beyond the 100-year time line has recently come up.  New Orleans' Hurricane Katrina experience is still fresh in our memories - less fresh is the commentary following it on beefing up defences for the 1000-year event (a category 5) instead of the 100-year event (another category 3).   As far as I can tell, they gave up on moving away from the 100-year mark - they can't even determine costing out a design to withstand the 1000-year event (here)