Was just reading this report on why the Japan quake was so large.

Apparently, current seismic understanding is that a fault typically only slips in isolated segments, but in the Japan quake, a number of different segments of the fault gave way together, resulting in the massive 9.0 quake. Sounds like that is primarily why seismologists had not predicted a larger quake (and resulting tsunami) to hit that region of Japan.

I'm curious if research like this will raise the hazard level of places like the Pacific Northwest or West Coast. That would be quite an economic cost if building codes were strengenthed for structures built in these areas.