1. Dept. of Civil and Environmental Engineering, The Hong Kong Univ. of Science and Technology, HKSAR, 999077, CN
2. Dept. of Civil and Environmental Engineering, The Hong Kong Univ. of Science and Technology, HKSAR, 999077, CN (Corresponding author), e-mail: ceyhwang@ust.hk
3. Dept. of Geology, The Univ. of Kansas, Lawrence, KS 66045 US