1. College of Geosciences, Guilin University of Technology, 39 Yanshan Road, Guilin 541004, China.
2. School of Civil Engineering, Guangzhou University, Guangzhou 510006, China.
3. Corresponding author.
4. Institute of Geophysics and Geomatics, University of Geosciences, Wuhan 430074, China.
5. Center for Northeast Asian Studies, Tohoku University, Sendai 980-8576, Japan.