1. Postdoctoral Research Fellow, The Earth Institute, Columbia Univ., 634A S.W. Mudd Bldg., 500W 120th St., New York, NY 10027. E-mail: franco@civil.columbia.edu
2. Professor, Dept. of Civil Engineering and Engineering Mechanics, Columbia Univ., 640 S.W. Mudd Bldg., 500W 120th St., New York, NY 10027. E-mail: betti@civil.columbia.edu
3. Assistant Professor, Dept. of Civil Engineering, Bogaziçi Univ., 34342 Bebek, Istanbul, Turkey. E-mail: hilmilus@boun.edu.tr