Three months have passed since the Great East Japan Earthquake triggered a nuclear crisis that shows little sign of ending anytime soon.

This is the fourth installment in a series that examines what caused the unprecedented crisis, which has dealt a fatal blow to the myth of the safety of nuclear power plants in this country.

"The lands of Mutsunokuni were severely jolted. The sea covered dozens, hundreds of blocks of land. About 1,000 people drowned."

This is a description of the massive Jogan Earthquake and tsunami that hit the Tohoku region about 1,150 years ago. It is contained in "Nihon Sandai Jitsuroku" (The official history of three reigns of Japan), which was compiled during the early Heian Period (794-1192).

Mutsunokuni is the name of the region that covered most of the present-day prefectures in the Tohoku region.

It is now clear the government and Tokyo Electric Power Co. did not learn from history.

Since 1990, Tohoku Electric Power Co., Tohoku University and the National Institute of Advanced Industrial Science and Technology have researched the traces left by the Jogan Earthquake. Their studies have shown that the ancient tsunami was on the same scale as that caused by the March 11 earthquake.