1. Department of Civil Engineering, Queen's School of Engineering, University of Bristol , Queen's Building, University Walk, Bristol, BS8 1TR, UK
2. Faculty of Environmental and Urban Engineering, Kansai University , 3-3-35 Yamate-cho, Suita, Osaka 564-8680, Japan
3. Disaster Prevention Research Institute, Kyoto University , Gokasho, Uji, Kyoto 611-0011, Japan