An Investigation of the Effect of Source Geometry on Grounded-Wire TEM Surveying with Horizontal Electric Field

Abstract

The grounded-wire transient electromagnetic (TEM) survey has been successfully applied in the mining industry to detect resources in the subsurface. Recently, research efforts have been devoted to developing both the theory and application of the short-offset TEM (SOTEM), which requires the layout of a line source for transmitting the electromagnetic signals. In practice, however, the terrain complexities of exploration areas, such as mountains and construction areas, often limit the layout of such linear geometry and moreover cause the source to be folded several times, which undesirably increases the computational differences especially when the line-source model is used for field data processing and interpretation. Therefore, to achieve high resolution TEM detection, it is now necessary to adapt the source layout to the local terrain. For describing the effect of source geometry on the SOTEM surveying, this study first presents a superposing-dipole approach for estimating the SOTEM field from arbitrarily-shaped sources and then qualifying the relative differences in the horizontal electric field due to varying source geometry. It is expected that such approach could be implemented for improving the TEM detection accuracy by taking into account all the turning points in a non-linear source layout, especially in the restricted areas. [Figure: see text]