Corporate Information

Press Release (Sep 28,2011)
Implementation of Boring and Trenching Survey on Yunotake Fault
We, Tokyo Electric Power Company, received an instruction document*1 from 
the Nuclear and Industrial Safety Agency (NISA) of the Ministry of Economy, 
Trade and Industry (NISA) on April 28. As a consequence of the occurrence 
of Tohoku-Chihou-Taiheiyou-Oki Earthquake, after which a huge crustal 
movement was observed, we have reviewed and summarized the Information 
regarding fault, which is necessary to take into consideration in the 
seismic design, which is necessary to review the possibility of eligibility 
to take into consideration in the seismic design of nuclear power station, 
for existing nuclear power station with existing survey and submitted to 
NISA on May 31, 2011.
                        (Previously announced on April 29 and May 31, 2011)

On June 6, 2011, we received an additional instruction document*2 regarding 
the above matter (Previously announced on June 6, 2011). Therefore, we 
conducted investigations on the amount of crustal movements and occurrence 
of earthquakes at the faults which we had evaluated that they need not to 
be considered for the seismic design. At the same time, we conducted ground 
reconnaissance and summarized a report regarding the faults of which we 
cannot deny the possibility that they fall into the faults which need to be 
considered for the seismic design and analyzed the influence upon the 
standard ground motion. Today we reported the results of our analysis to 
                                        (Previously announced on August 30)

Through the survey in relation to the report, we confirmed that a normal 
type of earthquake fault appeared along Yunotake Fault which had not been 
considered as an active fault in our seismic design. In order to survey the 
past activities of Yunotake Fault and study the causes and mechanism by 
which an earthquake fault appeared, we will start boring and trenching 
survey from September 29. 

Attachment:Overview of fault survey on Yunotake Fault(PDF 545KB)

*1 Instruction document
"Regarding the additional opinion of NISA for the analysis of reporting the 
results of evaluation of earthquake-proof safety of existing reactor 
facilities for power generation, referring to the new earthquake-proof 
standards established based on the Tohoku-Chihou- Taiheiyo-Oki Earthquake, 
2011 (Instruction)" 
(April 28, 2011 NISA No.4)

*2 Additional instruction document
"Regarding the response to the addition of opinions upon considered by NISA 
in relation to the report of the evaluation results on seismic safety of 
existing nuclear power reactor facilities etc. in light of the new Seismic 
Regulatory Guide based on the 2011 Tohoku District-Off the Pacific Ocean 
Earthquake (additional instruction)"
(June 3, 2011 NISA No.1)

We have provided a Japanese press release version of the instruction 
document received from NISA.  However, at this time we have reserved the 
right to not provide an English version due to potential misunderstandings 
that may arise from an inaccurate rendering of the original Japanese text.  
We may provide the English translation that NISA releases in our press 
releases. However, in principle we would advise you to visit the NISA 
website for timely and accurate information.
back to page top

to TOP