1. Institute of Geology and Geoinformation, Geological Survey of Japan, Advanced Industrial Science and Technology, Central 7, 1-1-1 Higashi, 305-8567, Tsukuba City, Ibaraki Prefecture, Japan
2. Department of Geography, Faculty of Letters, Komazawa University, 1-23-1Komazawa, 154-8525, Setagaya-ku, Tokyo, Japan