*Makoto OKUBO^1,5, Hirotaka Takahashi⁵, Akito Araya³, Satoshi Itaba², Masaki Kanao⁴ (1.Natural Science Cluster, Kochi University, 2.National Institute of Advanced Industrial Science and Technology, 3.Earthquake Research Institute, University of Tokyo, 4.National Institute of Polar Research, 5.Tokyo City University)