1. Lecturer, Dept. of Civil Engineering, Tsinghua Univ., Beijing 100084, China (corresponding author).
2. Dean, Cockrell School of Engineering, The Univ. of Texas at Austin, Austin, TX 78712.
3. Senior Researcher, E-Defense, National Research Institute for Earth Science and Disaster Prevention, Shinjimicho, Miki, Hyogo 673-0515, Japan.
4. Professor, Disaster Prevention Research Institute, Kyoto Univ., Gokasho, Uji, Kyoto 611-0011, Japan.