The Study About 1D Forward And Inversion Of Central-loop TEM

TEM has a lot of advantages than other geophysical methods and widely used in mineral exploration, water exploration, engineering and environment geophysical exploration. This paper aims at theory of Central-loop TEM, data processing and other aspects.The transient response of the 1D earth model excited by a circle loop is obtained by integrating the response of vertical magnetic dipole over the circle loop. The numerical filtering method is used to calculate forward modeling in frequency domain. By invert Fourier transformation, we used the linear sine and cosine transformation algorithm to obtain the transient response of layered forward modeling.Utilizing above algorithms, an computer program for 1D TEM forward modeling has been implemented. Using this program, we calculate 6 type model's EM response. From the numerical results, it is clearly show that layered media information is expressed by the shape of response curve, not by the characteristic points such as the peak points at the response curve, different the response curve shape, different the media structure. If the conductivity of above layer is greater than the lower layer, the information of lower layer is not sensitive to showing on the response curve.Discussing the features of the rapid inversion method based on"smoke"theory and the iterative inversion based optimization principle. The results show that when processing TEM data, the"smoke"theory inversion should be use at first for qualitative analysis, then on the basis of qualitative analysis the iterative inversion should be adopted for quantitative analysis. And an program for 1D TEM inversion modeling had been implemented based on LMF method.