1. Research Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology, Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan
2. JX Nippon Oil & Gas Exploration Corporation, 1-1-2 Otemachi 1-chome, Chiyoda-ku, Tokyo 100-8163, Japan