1. Graduate Research Assistant, Zachry Dept. of Civil Engineering, Texas A&M Univ., College Station, TX 77843-3136 (corresponding author).
2. Professor and Holder of the Buchanan Chair, Zachry Dept. of Civil Engineering, Texas A&M Univ., College Station, TX 77843-3136.
3. Associate Professor, Zachry Dept. of Civil Engineering, Texas A&M Univ., College Station, TX 77843-3136.
4. President, Fugro Geosciences Inc., 6100 Hillcroft Ave., Houston, TX 77081.