Earthquake ground motion is strongly influenced by site effects. Therefore, in the forthcoming edition of the technical standard for port and harbour facilities in Japan, it is recommended for engineers to take into account site effects appropriately in evaluating design ground motions. In this technical note,L2 design ground motions at typical 15 Japanese ports are evaluated, with site effects appropriately considered. First, scenario earthquakes, which are critical from seismic design point of view, are appropriately selected and macro and micro source parameters are evaluated based on geological information,etc. Then, L2 ground motions are simulated using a method proposed by Kowada et al.(1998), which takes into account empirical site amplification and phase characteristics. For this simulation, empirical site amplification factors are necessary. The authors basically used site amplification factors evaluated in the conventional study (Nozu and Nagao, 2005). At some ports,site amplification factors were newly evaluated based on spectral ratios
of observed ground motions at ports and those at nearby K-NET (Kinoshita,1998) stations.
　The result indicates that the above procedure allows us to evaluate L2 ground motions which clearly reflects site effects. The JMA seismic intensities, which are evaluated at the ground surface considering nonlinear site response, ranges from 5.0 (5+) to 6.4(6+), indicating the large variation in the intensity of L2 ground motion due to the large variability in site amplification factors. This emphasize the importance of accurate evaluation of site amplification factors for appropriate seismic design of structures. Short-period (1-3 years) observation of earthquake ground motions would be extremely useful for future seismic design of port structures.