A Research Of The Underground Electromagnetic Field In Three-dimensional Inclined Geological Body

This paper briefly introduced the basic principle of the E.M frequency sounding. On calculating the underground electromagnetic field in three-dimensional inclined anomalous body by the integral equation .The findings have carried on the beneficial exploration for underground E.M field of the horizontal harmonious electric dipole in the layered earth.This paper derived the expression of underground E.M field of the horizontal harmonious electric dipole in the layered earth ,the field survey method as well as the principle of digital filtering, at the same time the forward modeling programs for the E.M field in the upper and underground earth of the level harmonious electric dipole in the layered earth using the digital filtering method are coded. On calculating the electric field in three-dimensional inclined anomalous body, in order to do numerical calculation, At first, the three-dimensional inclined anomalous body is divided into N cubic element with the side length ?and supposed that the electric field in each element is constant. After obtaining the primary field value on the central point of each anomalous element, then transfer the Maxwell's equations into a matrix equation by using the integral equation and dyadic Green's function theory, and the anomalous field value has been obtained on the central point of each anomalous element by resolving the matrix equation. According to the reciprocity principle, on calculating the secondary field on the underground measuring point corresponding to the central point of each anomalous element, the E.M field expression is used on the earth's surface of the level harmonious electric dipole in the layered-earth. Finally, the primary field value was been work out on the underground measuring point by using the forward modeling programs of the horizontal harmonious electric dipole in the layered earth, then add it to the secondary field value produced by the anomalous electrical field on the underground measuring point corresponding to the central point of each anomalous element that to obtain the total field value of the level harmonious electric dipole.In this paper, the author investigated the E.M response property of the horizontal harmonious electric dipole on the underground of layered earth for three-dimensional inclined anomalous body by doing plenty of forward modeling calculation. According to the distribution characteristic of the underground apparent resistivity pseudo-section map of the frequency domain E.M sounding, the author mainly did the following research:1) On calculating the E.M response of three-dimensional inclined anomalous body in homogeneous half-space by using the integral equation forward modeling programs, the author investigated underground spatial distribution laws of anomalous. 2) The author investigated change law of the anomalous E.M field for three-dimensional inclined good conductor along with the buried depth of the top of the anomalous body, and estimated the underground detection capacity to three-dimensional inclined anomalous body of certain bulk. 3) The author investigated change law of the anomalous E.M field along with the dip angle of three-dimensional inclined good conductor by changing the dip angle of three-dimensional inclined good conductor in two-layer earth.