Mapping coalmine goaf using transient electromagnetic method and high density resistivity method in Ordos City, China

The research about subsurface characteristics by using transient electromagnetic method (TEM) and high density resistivity method (HDRM) were already conducted in Ordos. The objective of this research is to detect coalmine goaf areas based on rock resistivity. The data processing using wavelet transform, three point smoothing, RES2DINV and Maxwell processing software to obtain 2D resistivity structure. The results showed that the layers with maximum resistivity values (30–33 Ω m on Line 1, 30–31 Ω m on Line 2, 32–40 Ω m on Line 3) are founded at station 1–7, and 14–20 on Line 1,13–18 on Line 2, and 8–13 and 16–20 on Line 3 which is predicted as goaf layer, and the minimum resistivity values (20–26 Ω m of TEM, 45–75 Ω m of HDRM) at the other layers. This resistivity difference was caused by the geology and characteristics of the study area which is located close by the cleugh with rich coal, so the goaf area distinguishable with aquifer layer and coal seam. The results were also significant accidents and serious destruction of ecological environment.