TOKYO - In the country that gave the world the word tsunami, the Japanese nuclear establishment largely disregarded the potentially destructive force of the walls of water. The word did not even appear in government guidelines until 2006, decades after plants - including the Fukushima Daiichi facility that officials are still struggling to get under control - began dotting the Japanese coastline.

The lack of attention may help explain how, on an island nation surrounded by clashing tectonic plates that commonly produce tsunamis, the protections were so tragically minuscule compared with the nearly 14-meter tsunami that overwhelmed the Fukushima plant on March 11. The wave grew over three times as tall as the 4-meter bluff on which the plant had been built.

Japanese government and utility officials have repeatedly said that engineers could never have anticipated the magnitude 9.0 earthquake ? by far the largest in Japanese history . Even so, seismologists and tsunami experts say that according to readily available data, an earthquake with a magnitude as low as 7.5 - almost routine around the Pacific Rim - could have created a tsunami large enough to top the 4-meter bluff at Fukushima.

After an advisory group issued nonbinding recommendations in 2002, Tokyo Electric Power Company, the plant owner and Japan’s biggest utility, raised its maximum projected tsunami level at Fukushima Daiichi to between 5.4 and 5.7 meters - considerably higher than the 4-meter bluff. Yet the company appeared to respond only by raising the level of an electric pump near the coast by 20 centimeters, presumably to protect it from high water.

“We can only work on precedent, and there was no precedent,” said Tsuneo Futami, a former Tokyo Electric nuclear engineer who was the director of Fukushima Daiichi in the late 1990s. “When I headed the plant, the thought of a tsunami never crossed my mind.”

The intensity with which the earthquake shook the ground at Fukushima also exceeded the criteria used in the plant’s design, though by a less significant factor than the tsunami, according to data Tokyo Electric has given the Japan Atomic Industrial Forum, a professional group. Based on what is known now, the tsunami set off the nuclear crisis by flooding the backup generators needed to power the reactor cooling system.

For decades, though, Japanese officials and even parts of its engineering establishment clung to older scientific precepts for protecting nuclear plants, relying heavily on records of earthquakes and tsunamis, and failing to make use of advances in seismology and risk assessment since the 1970s.


Evolution of Designs

When Japanese engineers began designing their first nuclear power plants more than four decades ago, they turned to the past for clues on how to protect their plants. Official archives, some centuries old, contained information on how tsunamis had flooded coastal villages, allowing engineers to surmise their height.

So seawalls were erected higher than the highest tsunamis on record. At Fukushima Daiichi, officials at Tokyo Electric used a contemporary tsunami - a 3.2-meter high wave caused by a 9.5-magnitude earthquake in Chile in 1960 - as a reference point. The 4-meter-high cliff on which the plant was built would serve as a natural seawall, according to Masaru Kobayashi, an expert on quake resistance at the Nuclear and Industrial Safety Agency, Japan’s nuclear regulator.

Engineers took a similar approach with earthquakes. When it came to designing the Fukushima plant, official records dating from 1600 showed that the strongest earthquakes off the coast of present-day Fukushima Prefecture had registered between magnitude 7.0 and 8.0, Mr. Kobayashi said.

Those methods, however, did not take into account serious uncertainties like faults that had not been discovered or earthquakes that were gigantic but rare, said Greg S. Hardy, a structural engineer at Simpson Gumpertz & Heger who specializes in nuclear plant design and seismic risk, He visited Kashiwazaki after the 2007 quake as part of a study sponsored by the Electric Power Research Institute.

“We left it to the experts,” said Masatoshi Toyoda, a retired Tokyo Electric vice president who oversaw the construction of the plant. He added, “They researched old documents for information on how many tombstones had toppled over and such.”

Eventually, experts on government committees started pushing for tougher building codes. That pressure grew exponentially after the devastating Kobe earthquake in 1995, said Kenji Sumita, who was deputy chairman of the government’s Nuclear Safety Commission in the late 1990s. Mr. Sumita said power companies, which were focused on completing the construction of a dozen reactors, resisted adopting tougher standards .


Risks That Were Ignored

The first clear reference to tsunamis appeared in new standards for Japan’s nuclear plants issued in 2006.

The risk had received some attention in 2002, when the Japan Society of Civil Engineers published recommended tsunami guidelines for nuclear operators.

A study group at the society, including professors and representatives from utilities like Tokyo Electric, scrutinized data from past tsunamis, as well as fresh research on fault lines and local geography, to come up with the guidelines .

At the group’s last meeting, held just over a week before the recent tsunami, researchers debated the usefulness of three-dimensional simulations to predict the potential damage of tsunamis on nuclear plants, according to minutes from those meetings.

Perhaps the saddest observation by scientists outside Japan is that, even through the narrow lens of recorded tsunamis, the potential for easily overtopping the anti-tsunami safeguards at Fukushima should have been recognized.

In 1993 a magnitude 7.8 quake produced tsunamis with heights greater than 9 meters off Japan’s western coast, spreading wide devastation.

And even the distant past was yielding information that could have served as fresh warnings. Two decades after Fukushima Daiichi came online, researchers poring through old records estimated that a quake had actually produced a tsunami that reached nearly two kilometers inland in an area just north of the plant. That tsunami struck in 869.


By NORIMITSU ONISHI and JAMES GLANZ