The biggest lie to come out of the Japan earthquakes is: "Everything was working swimmingly, until the basement generators were flooded." Our own nuclear people have used this, since it is so comforting. No need to worry about earthquakes, as long as you aren't on the ocean.
A source at Tepco admitted it was possible that key facilities were compromised before the tsunami.
"The quake's tremors may have caused damage to the pressure vessel or pipes," the official said.
I must emphasize that this was a very low level of shaking, around 10 cm/s. Your house wouldn't even crack at this level. Now, we are talking horrible boiling water reactors, which are like glass inside, but now we know that engineering analysis is crap, which I've always suspected.
Unfortunately, to have a meltdown at 10 cm/s means that all US plants of this type are not worthy to be operating, since the 1 in 500 chance for all of the East is probably over that. Meltdown is supposed to be 1 in 10 million. Of course, we now expect our local people to stand up, blue in the face, and say we cannot expect any earthquakes here, and so what if the reactors are fragile to the point of ridiculousness. After all, they just passed a hand-waving safety review!
We can now add a lowest point to our fragility chart.
10 cm/s - nuclear meltdown
30 cm/s - cheap condos tilted, plaster cracked on houses
50 cm/s - bricks fly, houses damaged
70 cm/s - cheap condos fall over, houses destroyed
100 cm/s - normal buildings damaged.
Despite all these new findings, our happy engineers will stick to conventional analysis, and use peak ground acceleration instead. :)