1. School of Earth Science and Geological Engineering, Sun Yat-sen University, Guang Zhou, CN, e-mail: cegaoyan@gmail.com
2. Dept. of Civil and Environmental Engineering, The Hong Kong Univ. of Science and Technology, HKSAR, CN (Corresponding author), e-mail: ceyhwang@ust.hk
3. Dept. of Civil and Environmental Engineering, The Hong Kong Univ. of Science and Technology, HKSAR, CN, e-mail: junkangchow@gmail.com