By YURI KAGEYAMA and JUSTIN PRITCHARD, Associated Press Yuri Kageyama And Justin Pritchard, Associated Press – 1 hr 7 mins ago

TOKYO – In planning their defense against a killer tsunami, the people running Japan's now-hobbled nuclear power plant dismissed important scientific evidence and all but disregarded 3,000 years of geological history, an Associated Press investigation shows.

The misplaced confidence displayed by Tokyo Electric Power Co. was prompted by a series of overly optimistic assumptions that concluded the Earth couldn't possibly release the level of fury it did two weeks ago, pushing the six-reactor Fukushima Dai-ichi complex to the brink of multiple meltdowns.

Instead of the reactors staying dry, as contemplated under the power company's worst-case scenario, the plant was overrun by a torrent of water much higher and stronger than the utility argued could occur, according to an AP analysis of records, documents and statements from researchers, the utility and the Japan's national nuclear safety agency.

And while TEPCO and government officials have said no one could have anticipated such a massive tsunami, there is ample evidence that such waves have struck the northeast coast of Japan before — and that it could happen again along the culprit fault line, which runs roughly north to south, offshore, about 220 miles (350 kilometers) east of the plant.

TEPCO officials say they had a good system for projecting tsunamis. They declined to provide more detailed explanations, saying they were focused on the ongoing nuclear crisis.

What is clear: TEPCO officials discounted important readings from a network of GPS units that showed that the two tectonic plates that create the fault were strongly "coupled," or stuck together, thus storing up extra stress along a line hundreds of miles long. The greater the distance and stickiness of such coupling, experts say, the higher the stress buildup — pressure that can be violently released in an earthquake.

That evidence, published in scientific journals starting a decade ago, represented the kind of telltale characteristics of a fault being able to produce the truly overwhelming quake — and therefore tsunami — that it did.

On top of that, TEPCO modeled the worst-case tsunami using its own computer program instead of an internationally accepted prediction method.

It matters how Japanese calculate risk. In short, they rely heavily on what has happened to figure out what might happen, even if the probability is extremely low. If the view of what has happened isn't accurate, the risk assessment can be faulty.

That approach led to TEPCO's disregard of much of Japan's tsunami history.

In postulating the maximum-sized earthquake and tsunami that the Fukushima Dai-ichi complex might face, TEPCO's engineers decided not to factor in quakes earlier than 1896. That meant the experts excluded a major quake that occurred more than 1,000 years ago — a tremor followed by a powerful tsunami that hit many of the same locations as the recent disaster.

A TEPCO reassessment presented only four months ago concluded that tsunami-driven water would push no higher than 18 feet (5.7 meters) once it hit the shore at the Fukushima Dai-ichi complex. The reactors sit up a small bluff, between 14 and 23 feet (4.3 and 6.3 meters) above TEPCO's projected high-water mark, according to a presentation at a November seismic safety conference in Japan by TEPCO civil engineer Makoto Takao.

"We assessed and confirmed the safety of the nuclear plants," Takao asserted.

However, the wall of water that thundered ashore two weeks ago reached about 27 feet (8.2 meters) above TEPCO's prediction. The flooding disabled backup power generators, located in basements or on first floors, imperiling the nuclear reactors and their nearby spent fuel pools
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