1. Geotechnical Engineer, AMEC Geomatrix, 510 Superior Ave., Suite 200, Newport Beach, CA 92663.
2. Assistant Professor, Dept. of Civil and Environmental Engineering, Louisiana State Univ., 3531 Patrick F. Taylor Hall, Nicholson Extension, Baton Rouge, LA 70803.
3. Professor, Dept. of Structural Engineering, Univ. of California at San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0085 (corresponding author).