Analysis of multi-component response characteristics of the electrical source transient electromagnetic method

Abstract The electrical source transient electromagnetic (TEM) method has developed rapidly in the advantages of large detection depth, high efficiency, and complex terrain applicability. In recent years, most research on electrical source TEM focused on dBz/dt and Ex, while less attention has been paid to other components that have similar detection capabilities. In this paper, based on the layered model multi-component modelling method, we analysed the detection ability of each component and the influence of offset on the low- and high-resistance layers. Then, based on the time-domain vector finite element method, combined with parallel solver and SAI-Krylov subspace technology, we developed a 3D fast forward algorithm. 3D complex low and high-resistance models are simulated, and the resolution of each component to low and high resistance is discussed. The layered and 3D results show that: Ex is a negative anomaly for both low- and high-resistance bodies, and cannot distinguish between high and low resistance; dBy/dt has strong detection ability for both low- and high-resistance anomalies; dBy/dt, dBz/dt and Ex easily cause false anomalies; and all components could cause a detection blind spot with the increase of offset. In face of complex detection environments and different detection targets, understanding these points is helpful for optimizing the field design scheme, and improving the accuracy of data processing and resolution.