1. School of Automation, Northwestern Polytechnical University, Xi’an 710129, China
2. School of Earth and Space Science, Peking University, Beijing 100871, China
3. Institute of Geophysics, China Earthquake Administration, No. 5 Minzu Daxue Nan Road, Haidian District, Beijing 100086, China
4. Shanghai Sheshan National Geophysical Observatory, Shanghai 201602, China