1. Visiting Assoc. in Civ. Engrg., W. M. Keck Lab. of Hydr. & Water Resources, California Inst. of Tech., Pasadena, Calif. 91125
2. Grad. Research Asst., W. M. Keck Lab. of Hydr. & Water Resources, California Inst. of Tech., Pasadena, Calif. 91125
3. Prof. of Civ. Engrg., W. M. Keck Lab. of Hydr. & Water Resources, California Inst. of Tech., Pasadena, Calif. 91125