Seismologist testifies Fukushima nuclear disaster preventable — The Mainichi

” TOKYO — A seismologist has testified during the trial of three former executives of Tokyo Electric Power Co. (TEPCO), operator of the tsunami-ravaged nuclear plant, that the nuclear crisis could have been prevented if proper countermeasures had been taken.

“If proper steps had been taken based on a long-term (tsunami) evaluation, the nuclear accident wouldn’t have occurred,” Kunihiko Shimazaki, professor emeritus at the University of Tokyo, told the Tokyo District Court on May 9.

Shimazaki, who played a leading role in working out the national government’s long-term evaluation, appeared at the 11th hearing of the three former TEPCO executives as a witness.

Prosecutors had initially not indicted the three former TEPCO executives. However, after a prosecution inquest panel consisting of members of the public deemed twice that the three deserve prosecution, court-appointed lawyers serving as prosecutors indicted the three under the Act on Committee for Inquest of Prosecution.

Court-appointed attorneys insist that former TEPCO Vice President Sakae Muto, 67, and others postponed implementing tsunami countermeasures based on the long-term evaluation, leading to the disaster.

The government’s Headquarters for Earthquake Research Promotion released its long-term evaluation in 2002 predicting that a massive tsunami could occur along the Japan Trench including the area off Fukushima.

In 2008, TEPCO estimated that a tsunami up to 15.7 meters high could hit the Fukushima No. 1 power station, but failed to reflect the prediction in its tsunami countermeasures at the power station.

The Cabinet Office’s Central Disaster Prevention Council also did not adopt the long-term evaluation in working out its disaster prevention plan.

Shimazaki, who was a member of the Headquarters for Earthquake Research Promotion’s earthquake research panel in 2002, told the court that the Cabinet Office pressured the panel shortly before the announcement of the long-term evaluation to state that the assessment is unreliable. The headquarters ended up reporting in the long-term evaluation’s introduction that there were problems with the assessment’s reliability and accuracy.

In his testimony, Shimazaki pointed out that the Central Disaster Prevention Council decision not to adopt the long-term evaluation led to inappropriate tsunami countermeasures.

With regard to factors behind the council’s refusal to accept the evaluation, Shimazaki stated that he can only think of consideration shown to those involved in the nuclear power industry and politics.

“If countermeasures had been in place based on the long-term evaluation, many lives would’ve been saved,” Shimazaki told the court.

Shimazaki served as deputy chairman of the government’s Nuclear Regulatory Authority after the Fukushima nuclear disaster.

(Japanese original by Epo Ishiyama, City News Department, and Ei Okada, Science & Environment News Department) “

published in The Mainichi



Earthquake offshore of Japan shakes crippled Fukushima Nuclear Power Plant — Temblor

” At 9:11 a.m. local time today, a M=5.8 earthquake struck offshore of Japan, near the Fukushima Nuclear Reactor, which was crippled in the M=9 Tohoku earthquake in 2011. Fortunately this quake was not large enough to cause any new damage to the reactor, which is expected to take at least four decades to dismantle. Two of the reasons why no damage occurred is because the quake was offshore and at a depth of 35 km, meaning only light shaking was felt in populated centers of Iwaki (Pop: 357,000) and Fukushima (Pop: 294,000). The USGS PAGER system estimates that should there be any economic losses, they will remain extremely minimal.

Japan is one of the most seismically active countries on earth. Just off the eastern coast of the country are two subduction zones. In the southern part of the country is the Nansei-Shoto (Ryukyu) Trench, where there Philippine Sea plate subducts beneath the Eurasian Plate at rates varying from 47-61 mm/yr. To the north, is the Japan Trench, where the Pacific Plate subducts beneath the North American Plate at rates as high as 90 mm/yr (See USGS map below). What is also evident in this map is that northern Japan is much more seismically active than the southern portion of the country. While much of this can be attributed to aftershocks from the M=9.0 Tohoku earthquake there is still a greater rate of seismicity in the north. Based on the location of today’s M=5.8 earthquake, and its shallowly-dipping thrust focal mechanism, it likely occurred on the subducting slab, making this a late aftershock of the 2011 Tohoku quake.

In terms of the seismic hazard of Japan, there are two schools of thought, which are heavily related to the recent seismicity and convergence rates. Below is a comparison of the Global Earthquake Activity Rate (GEAR) model, which is available in Temblor, and the Japan National Hazard Model. The GEAR model uses seismicity from the last 40 years and global strain rates to forecast the likely earthquake magnitude in your lifetime anywhere on earth, while the Japanese model estimates the likelihood of strong ground shaking. What is immediately evident is that the models are almost opposite one another. The GEAR model sees the lack of earthquakes and slower convergence rates near the Nankai Trough as an indication of lower seismic potential, whereas the Japanese model interprets it as an increased likelihood of a large magnitude earthquake. While it is entirely possible that a large quake could strike along the Nankai Trough, it should be pointed out that the Japanese model misses the hazard near the M=9.0 Tohoku earthquake, while the GEAR model shows an extremely high hazard.

Regardless of which model better depicts the seismic hazard of Japan, what is clear is that nearly the entire eastern seaboard is susceptible to seeing M=6.75 earthquakes. This translates into an extremely high awareness among residents. It is because of this that Japan is at the forefront of seismic safety, and often considered the country after which other countries should model their earthquake preparedness. ”

by David Jacobson, Temblor

source with maps of the earthquake