A high level report on Fukushima Daiichi sequence of events was disclosed on July 26, 2012, due to the Freedom of Information Act, through the email which Shunsuke Kondo, the Chairman of Japan Atomic Energy Commition, sent to the key figures of Amrican nuclear industry. The title of the email is "Earthquake Impact". The report attatched in this email refers to the impact of the earthquake as the cause of the explosion of Fukushima Daiich Unit 1. TEPCO and the Japanese government, except the parliamentary report, have refused to admit the impact of the earthquake to the explosion of the power plants, rather attributing the cause to the unexpected tsunami.
In the text it says:
"It was reported at 15: 35 that the Reactor Building of 1F1 was ruptured after a rather strong earthquake with the sound of explosion and that the level of radiation at the site boundary was suddenly doubled from 500 micro Sv/hr of that after venting operation to 1 mSv/hr. The explosion is considered due to explosion of hydrogen leaked from the primary coolant boundary caused by the impact of the earthquake."
Read the full text on Enformable Nuclear News here