Kodai Yamaguchi, Chiba University, Chiba, Japan, Hitoshi Irie, Center for Environmental Remote Sensing, Chiba University, Chiba, Japan, Toshihiko Takemura, Kyushu University, Research Institute for Applied Mechanics, Fukuoka, Japan, Pradeep Khatri, Tohoku University, Sendai, Japan and Hirokazu Yamamoto, Geological Survey of Japan, AIST, Tsukuba, Japan