1. Lanzhou Institute of Seismology, China Earthquake Administration, No. 450 Donggang West Road, Chengguan District, Lanzhou 730000, Gansu Province, China, weicx12@163.commanzhongqin@eyou.comezhangys2011@163.comzrzr0115@163.comguox@gsdzj.gov.cnliuxzh@gsdzj.gov.cn1012860722@qq.com1044869778@qq.com
2. Also at Lanzhou Base of Institute of Earthquake Science, China Earthquake Administration, Lanzhou, China.
3. National Time Service Center, Chinese Academy of Sciences, Xi’an, China.
4. Corresponding author.
5. Petroleum Engineering Department, Colorado School of Mines, Golden, Colorado 80401 U.S.A., 27stones@163.com