1. Assistant Professor, Dept. of Civil and Environmental Engineering, Hong Kong Univ. of Science and Technology, Clearwater Bay, Kowloon, Hong Kong (corresponding author).
2. Principal Engineer, Rutherford & Chekene Consulting Engineers, 55 Second Street, Suite 600, San Francisco, CA 94105.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of California, Berkeley, CA 94720.