[1] Institute of Geophysics, National Central University, Chung-Li, Taiwan
[2] Institut de Physique du Globe, CNRS URA323, 67084 Strasbourg, France
[3] Jet Propulsion Laboratory, Pasadena, CA 91109, United States
[4] Institute of Oceanography, National Taiwan University, P.O. Box 23-13, Taipei, Taiwan