Hiroshima University ; Hiroshima University
DGDA ; Institut de physique du globe de Strasbourg (IPGS) ; CNRS - INSU - Université de Strasbourg - CNRS - INSU - Université de Strasbourg
This research is supported by the Ministry of Education
Science and Technology (MEXT) through Special Coordination Funds "Ridge Flux" and "Archaean Park" projects.