1. State Key Laboratory of Coal Resources and Safety Mining, China University of Mining and Technology, Beijing 100083, China
2. College of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083, China. Email: chnzenghu@gmail.com
3. Huaneng Coal Technology Research Co. Ltd, Beijing 100070, China
4. Shanxi Lanyan Coalbed Methane Group Co. Ltd, Jincheng 048000, China
5. Rock Physics Laboratory, Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77004, USA