That year, as Hamaoka’s No. 1 reactor started operating and No. 2 was under construction, Katsuhiko Ishibashi, a seismologist and now professor emeritus at Kobe University, publicized research showing that the plant lay directly above an active earthquake zone where two tectonic plates met. Over the years, further research would back up Mr. Ishibashi’s assessment, culminating in a prediction last year by the government’s own experts that there was a nearly 90 percent chance that a magnitude 8.0 quake would hit this area within the next 30 years.

After the 1995 Kobe earthquake, residents in this area began organizing protests against Chubu Electric. They eventually sued the utility in 2003 to stop the plant’s reactors, which had increased to four by then, arguing that the facility’s quake-resistance standards were simply inadequate in light of the new seismic predictions.

In 2007, a district court ruled against the plaintiffs, finding no problems with the safety assessments and measures at Hamaoka. The court appeared to rely greatly on the testimony of Haruki Madarame, a University of Tokyo professor and promoter of nuclear energy, who since April 2010 has been the chairman of the Nuclear Safety Commission of Japan, one of the nation’s two main nuclear regulators.

Testifying for Chubu Electric, Mr. Madarame brushed away the possibility that two backup generators would fail simultaneously. He said that worrying about such possibilities would “make it impossible to ever build anything.” After the Fukushima Daiichi disaster, Mr. Madarame apologized for this earlier comment under questioning in Parliament. “As someone who promoted nuclear power, I am willing to apologize personally,” he said.

In the early days of nuclear power generation in Japan, the government and nuclear plant operators assured the public of the safety of plants by promising that they would not be located on top of active fault lines, Mr. Ishibashi, the seismologist, said in an interview.

But he said that advances in seismology have led to the gradual discovery of active fault lines under or near plants, creating an inherent problem for the operators and the government and leading to an inevitable conclusion for critics of nuclear power.

“The Japanese archipelago is a place where you shouldn’t build nuclear plants,” Mr. Ishibashi said.

Advances in seismology also led to lawsuits elsewhere. Only two courts have issued rulings in favor of plaintiffs, but those were later overturned by higher courts. Since the late 1970s, 14 major lawsuits have been filed against the government or plant operators in Japan, which until March 11 had 54 reactors at 18 plants..