1. Assistant Professor, Dept. of Civil and Environmental Engineering, The Pennsylvania State Univ., 212 Sackett Building, University Park, PA 16802 (corresponding author).
2. Senior Research Scientist, Dept. of Geology, Univ. of Illinois at Urbana-Champaign, 245 Natural History Building, 1301 W. Green St., Urbana, IL 61801.
3. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois at Urbana-Champaign, 3215 Newmark Civil Engineering Laboratory, 205 N. Mathews Ave., Urbana, IL 61801.