1. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of California, Los Angeles, CA 90095-1593 (corresponding author).
2. Project Engineer, CH2M Hill, 6 Hutton Centre Dr., Santa Ana, CA 92707.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of California, Davis, CA 95616.
4. Associate Director, Center for Geotechnical Modeling, Univ. of California, Davis, CA 95616.