Japan has long tried to be proactive in regards to earthquakes, and tsunamis.
Many of their buildings are made to sway,and there are limitations on how high certain structures can be built.

The problem with some of the nuclear power plants is their location. Too close to the coast for such a geologically active region. They have made updates to many safety systems, and last I read, they shut down all but two reactors today until the tsunami threat subsides.

However, like most businesses, they have not been willing to dig deep enough financially for the worst case scenario.

They are better prepared than last time, but if the tsunami is big enough, it would still be cataclysmic, like before.