1. Assistant Professor. Dept. of Forest Engineering, Resources and Management, Oregon State Univ., 280 Peavy Hall, Corvallis, OR 97331; formerly, Ph.D. Candidate, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., New York, NY 10027 (corresponding author).
2. Professor of Civil Engineering, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., New York, NY 10027.