1. Ph.D. Candidate, Dept. of Civil Engineering and Engineering Mechanics, Univ. of Arizona, Tucson, AZ 85721.
2. Professor, Dept. of Civil Engineering and Engineering Mechanics, Univ. of Arizona, Tucson, AZ 85721.
3. Research Professor, Research Center for Disaster Prevention Science and Technology, Korea Univ., Seoul 136-713, Korea (corresponding author).