1. Principal Software Engineer, Geosoft Pte. Ltd., 2 Kaki Bukit Place, #07-00 Tritech Building, Singapore 416180; formerly, Ph.D. Student, Dept. of Civil Engineering, National Univ. of Singapore, Singapore 117576 (corresponding author).
2. Professor, Dept. of Civil and Environmental Engineering, National Univ. of Singapore, Singapore 117576.
3. Professor, Dept. of Mathematics, National Univ. of Singapore, Singapore 119076.