The tsunami that crippled the Fukushima No. 1 nuclear plant on March 11 reached a height of 13.1 meters and the waves that hit the nearby No. 2 plant were up to 9.1 meters, Tokyo Electric Power Co. said Friday based on the results of simulations.
The simulations indicated that the roughly 4-meter difference in wave heights at the two plants may have been due to several smaller tsunami that repeatedly struck at shorter intervals on the coasts of Miyagi and Fukushima prefectures.
The simulations divided the coast between Iwate and Chiba prefectures into 90 blocks, with six blocks off Miyagi and Fukushima considered strongly related to the tsunami that hit the plants, Tepco said.
The 13-meter tsunami reached the No. 1 plant 51 minutes after the 9-magnitude quake, while the 9-meter one reached the No. 2 plant after 48 minutes, the simulation shows.
It also shows that many locations at the No. 1 plant sustained flooding in excess of 3 meters, resulting in the loss of all alternating-current power and most of the backup diesel power generators.
The damage to the emergency power source was smaller at the No. 2 plant, where all four reactors had been shut down with their coolant temperature lower than 100 degrees.
Tepco had presumed that no tsunami would exceed 5.7 meters at the Fukushima plants.