1. Professor, Dept. of Structural Engineering, Univ. of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093 (corresponding author).
2. Senior Engineer, Saiful/Bouquet Consulting Inc., 385 E. Colorado Blvd., Suite 200, Pasadena, CA 91101.
3. Geotechnical Engineer, URS Corporation, 1333 Broadway, Suite 800, Oakland, CA 94612.
4. Professor, Dept. of Structural Engineering, Univ. of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093.