1. Disaster Prevention Research Institute, Kyoto University, Uji, Kyoto 611-0011, Japan
2. Graduate School of Engineering, Kyoto University, Uji, Kyoto 611-0011, Japan
3. Sumitomo Heavy Industries, Ltd., Shinagawa, Tokyo 141-6025, Japan
4. Tokyo Electric Power Company Holdings, Inc., Chiyoda, Tokyo 100-8560, Japan