1. RIKEN Advanced Institute for Computational Science, 7-1-26, Minatojima-minami-machi, Kobe 6500047, Japan
2. Department of Civil Engineering, Kobe University, 1-1, Rokkodai-cho, Nada-ku, Kobe 6578501, Japan
3. Earthquake Research Institute, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 1130032, Japan