1. Boise State University, Dept of Geosciences, 1910 University Drive, Boise, Idaho 83725, USA
2. Drexel University, Dept of Civil Engrg, 3141 Chestnut Street, Philadelphia, PA 19104, USA
3. City College New York Dept of Civil Engrg, 160 Convent Avenue, New York, NY 10031, USA