1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan, China
2. Department of Geography, Dartmouth College, Hanover, NH, US
3. State Key Laboratory of Resources and Environmental Information System (LREIS), Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
4. University of Chinese Academy of Sciences, Beijing China