1. School of Geography and Oceanography, Minjiang University, Fuzhou 350108, China
2. School of Geological Engineering and Geomatics, Chang’an University, Xi’an 710054, China
3. Roy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, TX 75275, USA
4. The Second Monitoring and Application Center, China Earthquake Administration, Xi’an 710054, China