Taken from boingboing:

Fukushima reactor 1 exploded
Photo by Reuters

Documents from Tokyo Electric, the operator of the Japanese nuclear plants in crisis after Friday’s devastating quake and tsunami, reveal that the company tested the Fukushima plant to withstand a quake up to magnitude 7.9. That threshold is well below the force of Friday’s quake, recently upgraded to 9.0.

Snip from Wall Street Journal:

Tepco’s last safety test of nuclear power plant Number 1–one that is currently in danger of meltdown–was done at a seismic magnitude the company considered the highest possible, but in fact turned out to be lower than Friday’s quake. The information comes from the company’s “Fukushima No. 1 and No. 2 Updated Safety Measures” documents written in Japanese in 2010 and 2009. The documents were reviewed by Dow Jones. The company said in the documents that 7.9 was the highest magnitude for which they tested the safety for their No. 1 and No. 2 nuclear power plants in Fukushima.

Thousands of evacuees from areas around Japan’s Fukushima nuclear power plant were scanned for radiation exposure, though the Japanese government insists radiation levels are low. Video courtesy of Reuters

Simultaneous seismic activity along the three tectonic plates in the sea east of the plants–the epicenter of Friday’s quake–wouldn’t surpass 7.9, according to the company’s presentation.

Link.

Edit 2011/03/14: seems that the contents on the Washington Journal page has changed and does no longer include the quoted text. (Thank you for noticing Boudewijn). However the information can be found on a couple of other websites: here and here.

See also:

Fukushima I Nuclear Power Plant
2011 Sendai earthquake and tsunami
Nuclear power accidents by country