1. Graduate Student, Dept. of Civil Engineering, Univ. of Minnesota, Minneapolis, MN 55455.
2. Research Fellow, E-Defense, National Research Institute for Earth Science and Disaster Prevention, Miki, Hyogo 673-0515, Japan.
3. Professor, Dept. of Civil Engineering, Univ. of Minnesota, Minneapolis, MN 55455.
4. Professor, Dept. of Civil Engineering, Univ. of Minnesota, Minneapolis, MN 55455 (corresponding author).
5. Professor Emeritus, Dept. of Civil Engineering, Univ. of Minnesota, Minneapolis, MN 55455.