1. Research Associate, Earth Sciences, Univ. College London, Kathleen Lonsdale Bldg., Gower St., London WC1E 6BT, U.K. (corresponding author).
2. Professor of Geotechnical Engineering, Dept. of Civil and Architectural Engineering, City Univ. of Hong Kong, Kowloon, Hong Kong.
3. Associate Professor, National Technical Univ. of Athens, Iroon Polytechniou 9, 15780 Zografou, Greece.