TEPCO compiled a record of observed seismic data collected from the base
mat of the reactor buildings (The lowest basement) at Fukushima Daiichi
nuclear power station and Fukushima Daini nuclear power station when the
Tohoku-Taiheiyou-Oki Earthquake occurred at 2:46pm on March 11, 2011.

We have collected and studied seismic data, and have compiled the
currently available acceleration time history data from each observation
point. These results have been reported to the Japanese Government.
                        (Previously announced on April 1 and May 16, 2011)

Today we have received an instruction document * "regarding actions
following the analysis of seismic data collected at Fukushima Daiichi
nuclear power station and Fukushima Daini nuclear power station during the
Tohoku-Taiheiyou-Oki Earthquake" from NISA. Following the instruction, we
will conduct detailed evaluation of the impact from the earthquake shake,
consider countermeasures for malfunction of seismometer, and report their
result to NISA.

*Actions following the analysis of seismic data collected at Fukushima
 Daiichi nuclear power station and Fukushima Daini nuclear power station
 during the Tohoku-Taiheiyou-Oki Earthquake (Instruction)
                                                     NISA No.6, 2011 May 6

On May 16, NISA received TEPCO's report of analysis of observed seismic
data collected at Fukushima Daiichi nuclear power station and Fukushima
Daini nuclear power station during the Tohoku-Taiheiyou-Oki Earthquake.

According to the report, acceleration response spectra of observed seismic
data observed at free foundation point in the reactor buildings in
Fukushima Daiichi nuclear power station was mostly below the acceleration
response spectra for evaluation of basic earthquake ground motion Ss in
most periods, however, spectra collected in Unit 2, 3, and 5 exceeded
spectra for evaluation by 30% at maximum during 0.2 to 0.3 seconds. 
Based on TEPCO's analysis above, NISA considers that it is extremely
important to evaluate the impacts from the earthquake on reactor buildings,
turbine buildings, and major facilities and pipes from earthquake
resistance perspective in Fukushima Daiichi and Daini nuclear power
station in order to confirm the status of safety function of those
facilities at the time of earthquake and following period.
The report also states that data recording was interrupted in several
voluntary located seismometers during 130 to 150 seconds after the
initiation of recoding due to the malfunction of recording devices.
The reason of malfunction was analyzed that 1) the program was coded to
finish the recording once the seismometer detects the shake below
threshold even if it detects the shake above such threshold afterwards, 2)
while the recording device was meant to restart the recording when the
shake exceeds threshold even after the recording was interrupted, program
didn't restart the recording due to the malfunction of recognition of
recording material. 
NISA accordingly requests TEPCO to report following matters by the
following due date.

1. Fukushima Daiichi and Diani nuclear power station
(1) Result of combining seismic response analysis of the impact from the
    shake of the earthquake on reactor building and their important
    facilities including PCV and RPV in Unit 2 and 4 of Fukushima Daiichi
    nuclear power station.
    Due date: June 17, 2011

(2) Result of combining seismic response analysis of the impact from the
    shake of the earthquake on reactor building and their important
    facilities including PCV and RPV in Unit 1 and 3 of Fukushima Daiichi
    nuclear power station.
    Due date: July 29, 2011

(3) Result of combining seismic response analysis of the impact from the
    shake of the earthquake on reactor building and their important
    facilities including PCV and RPV in Unit 5 and 6 of Fukushima Daiichi
    nuclear power station and in all units of Fukushima Daini nuclear
    power station and result of seismic response analysis of turbine
    buildings and major facilities and pipes from earthquake resistance
    perspective in both nuclear power station regarding the impact from
    the shake of the earthquake.
    Due date: August 17, 2011

2. Recording device allocated to collect seismic data
   Survey of the malfunction revealed in the report regarding the
   recording devices of all kinds of voluntary located seismometers in
   TEPCO's all nuclear power station and result of modification made
   following the survey. 
   Due date: June 17, 2011