The 2011 Tohoku earthquake and tsunami at 14:46 JST on 11 March 2011 affected large areas of the eastern and northern part of Japan, and many sea disasters of vessels moored in harbors occurred. We conducted surveys on two large tankers with mooring line breakage. During the surveys, the mooring line breakage happened due to not only the tsunami impact but also oscillations of dolphins by the seismic vibration. In this paper, we have composed a time domain model to estimate moored ship behavior due to oscillations of dolphins during earthquake, and investigated into the actual mooring line breakage of the VLCC at S-port, using the simulation model and the observed ship motion by GPS.
