1. Department of Geophysics, Graduate School of Science; Tohoku University; Sendai Japan
2. Deceased 21 December 2013
3. Department of Earth and Planetary Sciences; Tokyo Institute of Technology; Tokyo Japan
4. Department of Earth and Planetary Sciences, Faculty of Science; Kyushu University; Fukuoka Japan
5. Department of Earth and Environmental Sciences; Kumamoto University; Kumamoto Japan
6. Earthquake Research Institute; University of Tokyo; Tokyo Japan