1. International Research Institute of Disaster Science, Tohoku University , Aoba 468–1, Aramaki, Aoba-ku, Sendai 980-0845, Japan
2. Graduate School of Engineering, Tohoku University , Aoba 468–1, Aramaki, Aoba-ku, Sendai 980-0845, Japan
3. International Center for Urban Safety Engineering, The University of Tokyo , 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan