E-E_Φ Wide Field Electromagnetic Method Forward Modeling Study

The wild-field electromagnetic method presented by Professor He Jishan is a new kind of artificial frequency domain electromagnetic sounding method. This method adopts the formula of the accurate apparent resistivity without simplifying to calculate the apparent resistivity, that is getting the apparent resistivity value with required precision,through successive approximated the measured electric field value by the computer iterative method in the apparent resistivity formula, thus the precision and efficiency of the apparent resistivity we get are much improved than that of Cagniard apparent resistivity.At present, the key of theory and applied research in wild-field method is doing research on Ex component, in order to expand the theory and rich the field practical application of wild-field method, this paper makes the research of integral equation forward modeling with EΦ component in wild-field method. The paper introduces the basic theory, induces the apparent resistivity formula of EΦ component and the closed solution of electric field0component produced by horizontal electric dipole source in homogeneous half space. Based on wild-field method theory, using the integral equation to calculate the electric field value of EΦ component, and getting the wild-field apparent resistivity by computer iterative method, consequently gain the forward modeling results.In this paper, based on1D and3D numerical simulation, from the aspects of the electric field distribution, the detectability of layed stratum and single abnormal body, the static effect and the field source shadow effect, I make the research on EΦ component, carry on the contrastive analysis on the forward results of EΦ with the simulation results of Ex, Ey and Cagniard apparent resistivity, the EΦ forward modeling results can well reflect the real situation of the layered strata and low-resistance abnormal body, but is not sensitive to high resistance abnormal body, EΦ apparent resistivity’s static effect and source shadow effect is small than the Ex, Ey and Cagniard resistivity. The paper proposes the field observation equipment of wide-field electromagnetic EΦ component, and gives the contrast analysis of the measurement EΦ and Ex data. The results show that, EΦ component has unique advantages, in the detection range, and the reflected ability to the layered formation and the abnormal body, etc.