1. College of Geosciences and Surveying Engineering, China Univ. of Mining and Technology (Beijing), Beijing 100083, P. R. China.
2. College of Geosciences and Surveying Engineering, China Univ. of Mining and Technology (Beijing), Beijing 100083, P. R. China; State Key Laboratory of Coal and CBM Co-mining, Shanxi Jincheng Anthracite Mining Group Company, Ltd., Jincheng, Shanxi 048000, P. R. China (corresponding author).
3. Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education and School of Earth Resources, China University of Geosciences, Wuhan 430074, P. R. China; Energy & Geoscience Institute, Univ. of Utah, Salt Lake City, Utah 84108.