Historical data ignored.
The government ignored the history of previous quakes and tsunamis in the Tohoku region (including Fukushima Prefecture) and approved the construction of the plants.

In 869, July 13, the Jogan earthquake caused extensive damage in the region, and generated waves that left sand deposits as much as 2 kilometers (1,2 miles) inland. Descriptions in history texts suggest seismic thrust of magnitude c. 8.6.

Eastern and western Japan sit on different tectonic plates, with the Tohoku region sitting near the edge of a third. Experts calculated that an event the size of the one that hit in 869 were prone to take place every 800 to 1000 years.

Prof. Y. Suzuki, Research Center for Seismology, Volcanology and Disaster Mitigation, Nagoya Univ., told the Japan Times that safety measures were not sufficient. In 2005, extensive research determined that large tsunami could be generated of the tohuku coast; the government was in a position to take immediate action and ensure the safety of the nuclear power plants in Fukushima Prefesture. Warnings were based on historic fact as well as scientific date, Suzuki said.

So far, TEPCO has refused to admit that its precautions fell short. Fukushima plants 1 (Daiichi) and 2 (Daini) were designed to resist a 5.5 meter wave based on standards set by Japan Society for Civil Engineers. The utility said it simply didn't anticipate the 10-meter-plus tsunami. It claimed historical data were considered.

Other utilities-
Hokkaido Electric Power Co. announced that it will beef up tsunami measures at its Tomari nuclear plant, where current provisions are for a 9.8 meter wave. They had considerated that the 10 meter above sea level position would protect Tomari.

Experts point to the Hamaoka nuclear plant as being at the greatest risk, since it sits atop an area where a fourth plate meets Honshu's two main plates. A quake likely to exceed magnitude 8.0 is expected there. A major quake is expected every 150 years thers, the last, magnitude 8.4, hit in 1854.

CHIBU Electric Power revealed plans for a 12-meter wall around rhe Hamaoka complex. Damage there would be a "fatal blow" to Japan, said Kobe Univ. Prof. Ishibashi.

Experts point out that all plants need overhaul.

Above extracted from Japan Times, March 27, 2011, "Signs of Disaster Were There to See," Jun Hongo, staff writer.