1. Post-Doctoral Research Assistant, Dept. of Civil Engineering, Colorado State Univ., Fort Collins, CO 80523.
2. Professor, Dept. of Civil Engineering, Colorado State Univ., Fort Collins, CO 80523 (corresponding author).
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin-Madison, Madison, WI 53706.
4. Assistant Professor, Dept. of Earth and Environmental Sciences, Korea Univ., Anam-dong, Sungbuk-ku, Seoul, 136-701, Korea.
5. Professor, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin–Madison, Madison, WI 53706.