1. a Swiss Reinsurance Company , Mythenquai 50/60, P.O. Box, CH-8022, Zurich, Switzerland
2. b Laboratory of Hydraulic Constructions (LCH), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 18, CH-1015, Lausanne, Switzerland E-mail:
3. c Laboratory of Hydraulic Constructions (LCH), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 18, CH-1015, Lausanne, Switzerland
4. d Laboratory of Hydraulic Constructions (LCH), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 18, CH-1015, Lausanne, Switzerland E-mail: