Chisato Anai, Kyoto University, Aso Volcanological Laboratory, Kumamoto, Japan, Yasuo Miyabuchi Sr., Kumamoto University, Advanced science and technology, Kumamoto, Japan, Mitsuru Utsugi, Kyoto Univ., Kumamoto, Japan, Nobutatsu Mochizuki, Kumamoto University, Kumamoto, Japan, Hidetoshi Shibuya, Kumamoto Univ, Kumamoto, Japan and Takahiro Ohkura, Kyoto University, Kyoto, Japan