Naohito Otobe Department of Geophysics, Kyoto University Kyoto,Sakyou-ku,606-8502,Japan e-mail:otobe@kugi.kyoto-u.ac.jp
Satoshi Sakai School of Earth Sciences, IHS, Kyoto University Kyoto,Sakyou-ku,606-8501,Japan e-mail:sakai@gaia.h.kyoto-u.ac.jp
Shigeo Yoden Department of Geophysics, Kyoto University Kyoto,Sakyou-ku,606-8502,Japan e-mail:yoden@kugi.kyoto-u.ac.jp
Masato Shiotani Graduate School of Environmental Earth Science, Hokkaido University Sapporo, Kita-ku, 060-0810, Japan e-mail:shiotani@ees.hokudai.ac.jp