Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;
Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;
Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;
Earth Science Center of Graduate School, Chinese Academy of Sciences, Beijing 100039, China;
Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;
direct foreshock; generalized foreshock; ambient shear stress;