Abstract
Damage and influences to oil tanks caused by severe strong ground motion due to a large earthquake (Mw6.6) that occurred in the district of Iburi-tobu, Hokkaido, Japan on September 6, 2018 are reported in this paper. In the vicinity of the seismic source region, two large-scale crude-oil storage bases are located. The neighboring two bases had in total 86 large oil storage tanks with a capacity of 115,000 m3. The oil storage bases were hit by strong ground motion with peak ground accelerations of 590 to 1,570 cm/s2 and with peak ground velocities of 50 to 80 cm/s. Shell plates of a small bunker A tank with a capacity of 306 m3 suffered diamond buckling and elephant-foot buckling. No large oil storage tanks lost their function of oil storage despite of the severe strong ground motion. However, most of them splashed oil from the gap between the floating roof and the shell plate, and many of them had damage to their pontoons, gauge poles, guide poles, rolling ladders, liquid-level meters, and shoulders of foundation. One of the 115,000-m3-in-capacity tanks was equipped with a displacement gauge system to measure uplift of the bottom of the shell plate from the shoulder of tank foundation. The system recorded a maximum uplift of 4.4 cm. This is the world’s first record of uplift of a large tank caused by a natural earthquake.
A technique for simulating strong ground motion using hybrid Green's function
