Prospecting the Goaf Area of Coal Mine with Transient Electromagnetic Differential Imaging Method

Using transient electromagnetic sounding method to prospect conductive thin layers in the goaf area has equivalence phenomenon, making the inversion very difficult. The conventional optimization inversion method depends heavily on the initial model. If the initial model is not good, it is easy to get into local minimum. Besides, model parameters are sensitive to forward results, and the inversion often fails. In this paper, we have proposed a fast and effective transient electromagnetic sounding inversion method, apparent longitudinal conductance differential imaging. Both theory and practice have proved that, compared with apparent resisitivity method, this method is more intuitive, faster and it has higher resolution. The maging result agrees fairly well with the results of other inversion methods.