作者机构:[1]Department of Geophysics, School of Earth and Space Sciences, Peking University, Beijing 100871, China
相关基金:This work was partly supported by the National Fundamental Science Program of China under (No. 2004cb418406), the National Natural Science Foundation of China (No.90814002) and Key Projects in the National Science & Technology Pillar Program during the Eleventh Five-year Plan Period (No. 2008BAC38B02-4). We thank two anonymous reviewers for their helpful comments and suggestions on the manuscript.