1. Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China, kakayao@mail.ustc.edu.cndongzhi@mail.ustc.edu.cn
2. China Earthquake Networks Center, Beijing 100045, China, sunli@seis.ac.cn
3. Department of Geosciences, State University of New York at Stony Brook, Stony Brook, New York 11794 U.S.A., lianxing.wen@stonybrook.edu
4. Also at Laboratory of Seismology and Physics of Earth’s Interior, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.