Cheinway Hwang1, Emmy T Y Chang2. 1. Department of Civil Engineering, National Chiao Tung University, Hsinchu, Taiwan. cheinway@mail.nctu.edu.tw etychang@ntu.edu.tw. 2. Institute of Oceanography, National Taiwan University, Taipei, Taiwan. cheinway@mail.nctu.edu.tw etychang@ntu.edu.tw.