Picture of Tsunami wave hitting Japan at another location
The Fukushima power plants were required by regulators to withstand a certain height of tsunami. At the Daiichi plant the design basis was 5.7 metres (18.7 feet) and at Daini this was 5.2 metres (17.1 feet).
Tepco has now released tentative assessments of the scale of the tsunami putting it at over 10 metres (over 32.8 feet) 14 meters (46 feet) at Daiichi and over 12 metres (over 39.4 feet)14 meters at Dainii.
TEPCO believes the tsunami that inundated the Fukushima Daiichi site was 14 meters high, the network said. The design basis tsunami for the site was 5.7 meters, and the reactors and backup power sources were located 10 to 13 meters above sea level.
The plant sites were inundated, causing the loss of residual heat removal systems at both sites as well as emergency diesel generators at Daiichi.