Odin Marc, ETH Zurich, Zurich, Switzerland, Marielle Gosset, IRD, Toulouse, France, Hitoshi Saito, Kanto Gakuin University, College of Economics, Yokohama, Japan, Taro Uchida, University of Tsukuba, Tsukuba, Japan and Jean-Philippe Malet, Institut de Physique du Globe Strasbourg, Strasbourg Cedex, France