1. School of Geography and Earth Sciences, McMaster University, 1280 Main St W., Hamilton, Ontario, L8S 4K1, Canada,
2. École Polytechnique de Montréal, Département des génies civil, géologique et des mines, C.P. 6079, Succ. Centre-ville, Montréal, Québec, H3C 3A7, Canada,
3. Department of Civil Engineering, University of Toronto, 35 St George Street, Toronto, Ontario, M5S 1A4, Canada,