1. Institute of Geosciences, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka 422–8529, Japan.
2. Lanzhou Institute of Geology, Chinese Academy of Sciences, Lanzhou 730000, China.
3. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China.
4. Seismological Bureau of Qinghai Province, Xining, China.
5. Seismological Institute of Lanzhou, Lanzhou 730000, China.