1. Professor, Dept. of Civil Engineering, 603E CE/TTI Building, Texas A&M Univ., College Station, TX 77843-3135.
2. Graduate Research Assistant, Dept. of Civil Engineering, 601A CE/TTI Building, Texas A&M Univ., College Station, TX 77843-3135 (corresponding author).
3. Professor, Dept. of Geology and Geophysics, 309 M.T. Halbouty, Texas A&M Univ., College Station, TX 77843-3115.