1. Graduate School of Science, Kyoto University (currently OSPEC Inc.), Gokasho, Uji Kyoto 611‐0011 Japan
2. Disaster Prevention Research Institute Kyoto University, Gokasho (currently Fukada Geological Institute), Uji‐shi Kyoto 611‐0011 Japan
3. Civil Engineering Research Laboratory, Central Research Institute of Electric Power Industry (currently Hokkaido University), 1646 Abiko, Abiko‐shi Chiba 270‐1194 Japan
4. Research Institute for Natural Hazards and Disaster Recovery Niigata University, 8050 Ikarashi‐nino‐cho, Nishi‐ku Niigata 950‐2181 Japan