Tepco will reduce unit 2's injection rate by 4 tons/hour on 18 February.
The cause of the collapse of the Yonomori line tower No. 27 was underground water. The tower collapsed 2 minutes 30 seconds after the start of the earthquake. Underground water flows under the embankment. The ground became weaker as a consequence of shaking for a long time. The embankment was constructed during the 1965 - 1975 period to fill up a marsh, so there is much water. Tepco checked 530 towers concerning the Fukushima Daini and Kashiwazaki Kariwa plants, etc. but found no similar case.
"causes of damage situation of power facilities inside and outside of Fukushima Daiichi Nuclear Power" (2nd release) (Japanese, 15 pages)
"safety evaluation of transmission tower foundations regarding the offsite power supply to nuclear power stations and reprocessing plants" (Japanese, 17 pages)