1. Tech. Res. Inst., TOA Corp., 1-3 Anzen-cho, Tsurumi-ku, Yokohama 230, Japan; formerly, Fellow of Sci. and Technol. Agency, Port and Harbour Res. Inst., Japan; corresponding author. E-mail: ali@magical2.egg.or.jp
2. Deceased; formerly, Assoc. Prof., Dept.of Civ. Engrg., Yokohama Nat. Univ., 156, Tokiwadai, Hodogaya-ku, Yokohama 240, Japan.
3. Res. Engr., Tech. Res. Inst., TOA Corp., 1-3 Anzen-cho, Tsurumi-ku, Yokohama 230, Japan.