1. Assistant Professor, Dept. of Civil Engineering, The Catholic Univ. of America, Washington, DC 20064.
2. David H. Burrows Professor, The Charles E. Via, Jr. Dept. of Civil and Environmental Engineering, Virginia Polytechnic Institute and State Univ., Blacksburg, VA 24061.
3. Technical Staff Member, Statistical Sciences Group, Los Alamos National Laboratory, Los Alamos, NM 87544.