1. Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Science, Langfang 065000, China
2. National Research Center of Geo-Exploration Technology, Langfang 065000, China
3. Key Laboratory of Geophysical Electromagnetic Probing Technologies of Ministry of Natural Resources, Langfang 065000, China
4. Department of Geo-Exploration and Science Technology, Jilin University, Changchun 130026, China