The March 2011 tsunami that crippled the Fukushima No. 1 nuclear power plant was foreshadowed almost 10 years earlier, but government interference meant the threat was not acted on, seismologist Kunihiko Shimazaki has said.
Shimazaki said a July 2002 prediction by the Headquarters for Earthquake Research Promotion stated an earthquake as big as one in 1896 that caused monster tsunami had a 20 percent chance of occurring somewhere near the Japan Trench within 30 years.
The trench lies in the Pacific and stretches off the Sanriku area in the Tohoku region to the Boso Peninsula off Chiba Prefecture.
The 1896 tsunami triggered by the temblor that struck off Sanriku killed some 22,000 people.
The prediction by the government panel covered areas including waters off Fukushima Prefecture, home to the Fukushima No. 1 plant, which suffered a triple reactor meltdown due to damage from the tsunami unleashed by the March 11, 2011, magnitude-9.0 earthquake that hit Fukushima and other parts in the Tohoku region.
“Compared with earthquakes that occur in active faults once in thousands of years, the probability (of 20 percent in 30 years) is surprisingly high and cannot be ignored,” Shimazaki, who played a central role in drawing up the long-term tsunami prediction and is now professor emeritus at the University of Tokyo, said.
However, he said that just before the release of a report on the prediction, the secretariat of the research headquarters added a paragraph stressing the uncertainty of the forecast.
“An official of the Cabinet Office responsible for anti-disaster measures insisted on having a different committee discuss long-term tsunami prediction,” he said. “This was something that had never happened before, and I felt pressure.” He added, “It was puzzling and frightening.”
Shimazaki said the Central Disaster Prevention Council (CDPC) of the Cabinet Office ended up making tsunami assumptions that were far removed from the prediction by the Headquarters for Earthquake Research Promotion.
The CDPC assumed that only the northern part of the Tohoku region would be hit by tsunami, based on the premise that a recurrence of the 1896 Sanriku earthquake would occur in the same place, explained Shimazaki.
Huge tsunami around the same location near the Japan Trench have occurred at intervals of hundreds of years, and only about 100 years have passed since the 1896 earthquake, he noted.
The CDPC, which is tasked with devising anti-disaster measures based on the government-affiliated research body’s long-term predictions, chose to focus on the low probability and turned its eyes away from waters off the southern part of the Tohoku region, including Fukushima and Ibaraki Prefecture, just south of Fukushima, Shimazaki said.
He admitted that it is difficult for seismologists to predict earthquakes and tsunami with perfect accuracy, saying that while temblors do take place repeatedly in the same area they occur in somewhat different locations.
But Shimazaki added, “We can make assumptions about the location, timing and size to some extent, within certain ranges.
“Such assumptions were made, but were not utilized for the Fukushima No. 1 plant,” he said.
Shimazaki, 70, has also served as chairman of the Coordinating Committee for Earthquake Prediction and acting chairman of the Nuclear Regulation Authority. At the NRA, he played a major role in the work to create the country’s stricter nuclear plant safety standards based on lessons from the Fukushima No. 1 disaster.
Last July, he appeared in court as a witness for plaintiffs suing the central government and Tepco over the nuclear disaster.
“A lot of people died in the quake and tsunami,” Shimazaki said. “I’m also responsible for failing to reduce the damage.”
Stressing that such a disaster that claimed so many lives must never be repeated, Shimazaki said, “We must find out why it happened, but the causes are not being pursued.”
“The mistakes will be repeated if nothing is done,” he said as he explained why he decided to speak in court.
He also said assumptions of tsunami occurring on the Sea of Japan side of the country, announced by a land ministry working group in 2014, were not sufficient.
“If a catastrophic disaster happens again, they might again claim that it was beyond their assumptions,” he said. “That can’t be permitted.”
Although five years have passed since the nuclear meltdowns, Shimazaki said he doubts anything has changed.
“I see lack of clarity and responsibility in committees of experts organized by the state,” he said.
“In the world of science, we can together look for facts and can reach agreement to a certain extent. That is not the case when the state is involved, and mistakes will be repeated if we are not aware of the difference.”
Science is used for decision-making by the state, but scientists do not challenge how this is done, he said.
“They have to say ‘no’ if they think something is wrong, but they are not doing this,” Shimazaki said, adding that the lack of clarity around responsibility remains in five years.