Field observation on wave, current and long-period motions of a moored vessel at Reihoku Port was conducted. Highly accurate data of six motions around the center of gravity of the vessel, the tension of the mooring ropes and the displacement of the fender were obtained. It was confirmed that the longperiod motions, such as surging, swaying and yawing, were strongly affected by mooring system. By considering multi-directionality and frequency bandwidth of incident waves as input conditions for a numerical simulation, the calculation results of the vessel motions agree with the field observation data well.
