1. Department of Geophysics, School of Earth and Space Sciences, Peking University, Beijing, China
2. Institute of Earthquake Forecasting, China Earthquake Administration, Beijing, China
3. China Earthquake Networks Center, China Earthquake Administration, Beijing, China
4. Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, Université d’Orléans, CNRS, Orléans, France