1) The plants withstood a 9.0 Earthquake with apparent ease. These are 40 year old reactors, and held up well. Newer reactors like those in the USA, are built on "rollers" to help them withstand even MORE severe of an earthquke as this was.
2) The reactors were shut-down in an orderly manner and the nuclear reaction was stopped.
3) A while later the Tsunami occurred, and we see where the major flaw was, having the diesel generators susceptible to the tsunami, not with a flaw in the reactor design.
4) The storage of the spent fuel pools at the top of the reactor was a big mistake. Although the nuclear hysteria is causing problems with spent fuel storage and probably has some blame.
5) The officials where slow to react and call in external assets(fire truck pumps) to help, which is probably a cultural thing.
If they would have put some more thought into the location of their generators and their spent fuel storage units, we would have had a zero incident.
Most likely we will have a few bannana's worth of radiation, a shit load of media hysteria, and 4 reactors that actually worked very well for being in a 9.0 earthquake and a massive tsunami.
And people will still be afraid of the cleanest and lowest cost energy source known to man.