1. 1Earth and Environmental Sciences Programme, Faculty of Science, The Chinese University of Hong Kong, Hong Kong S.A.R., China, 999077
2. 2Key Laboratory of Intraplate Volcanoes and Earthquakes, Ministry of Education, China University of Geosciences (Beijing), Beijing, China, 100083
3. 3National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan, 305-8567
4. 4Institute of Geophysics, China Earthquake Administration, Beijing, China, 100036