Affiliation: | International Institute of Seismology and Earthquake Engineering, Building Research Institute, Ministry of Construction, 1 Tatehara, Tsukuba, Ibaraki, 305-0802, Japan. E-mail:;, Department of Earth and Planetary Science, Graduate School of Science, Tokyo University, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan. E-mail: |