Identification of hydrogeological structure and inference of hydraulic parameters based on the magnetotelluric method

The magnetotelluric method has been widely used in the exploration of mineral resources and engineering survey for several years. However, this method is seldom employed in hydrogeological investigation. In this paper, we regard the thick Quaternary sediments in a sand dune-and-meadow interlaced region of Horqin as the research area, and analyze the application of the EH-4 exploration to the thick quaternary phreatic aquifer through the EH-4 magnetotelluric method system. By using the EH-4 data and particle size analyses we delineate the spatial distribution of the sandy clay layer in a depth of 105 m in the study area. We carry out a test on the results of the geophysical prospecting by using three peripheral borehole data, which show that the total error of the geophysical prospecting is between 5.1% and 7.2%. The results indicate that EH-4 has a good application effect on hydrogeological exploration in the thick Quaternary phreatic aquifer. To calculate the soil saturated hydraulic conductivity in the range of 105 m we use the existing Pedo-transfer function model in the study area, and obtain a fitting model of the saturated hydraulic conductivity and the apparent resistivity from the EH-4 magnetotelluric method in the saturated fresh water. The model results reveal the distribution of water yield property and saturated hydraulic conductivity with the depth range of 200 m in the study area. The quantitative interpretation of the EH-4 magnetotelluric method in hydrogeologic field is realized, which may provide more abundant information of the study area. At the same time, the scale of the hydro-geophysical method in hydraulic parameter prediction is greatly improved.