1. China Earthquake Networks Center (CENC), No.5. Sanlihenanheng Street, Xicheng District, Beijing 100045, China, meng.lingyuan@hotmail.com
2. Also at U.S. Geological Survey (USGS), Earthquake Science Center, Menlo Park, California 94025.
3. U.S. Geological Survey (USGS), Earthquake Science Center, Menlo Park, California 94025