1. Ph.D. Candidate, Dept. of Civil and Environmental Engineering, Univ. of California, Los Angeles, CA 90095-1593.
2. Associate Professor and Vice Chair, Dept. of Civil and Environmental Engineering, Univ. of California, Los Angeles, CA 90095 (corresponding author).
3. Professor and Chair, Dept. of Civil and Environmental Engineering, Univ. of California, Los Angeles, CA 90095.