東北地方太平洋沖地震による石油タンクのスロッシング被害と長周期地震動

抄録

The 2011 off the Pacific coast of Tohoku Earthquake (Mw9. 0) occurred on 11 March2011 caused various damage to oil storage tanks in wide area. At Sakata, Niigata, Kashima and Tokyo Bay area, we found damage due to the liquid sloshing excited by the long-period ground motions such as sinking of floating roofs, failure of pontoons, deformation of gauge poles, leakage of oil onto the floating decks, and so on. Many strong motion records were obtained in and around tank sites and their velocity response spectra Sv in the long-period range hardly exceed the regulation in the Fire Service Law at all. Therefore, the floating roofs reinforced in compliance with the technical standard of the Fire Service Law revised in consideration of the damage in the 2003 Tokachi-oki earthquake suffered no severe damage. On the other hand, unreinforced floating roof of a tank located in the Tokyo Bay area sank after 3 days of the event because of the failure of pontoons by the liquid sloshing, although Sv near the tank is not more than 100cm⁄s in the previous regulation.