Numerical Calculation Of Time-Domain Ground-Airborne Electromagnetic Response Of2D On Source Of Electrical

China has vast territory and rich natural resources. But with the rapiddevelopment of economic, we need more energy and resources for people’s dailylives. The resources in shallow earth are less and less, so we need probe deeper earth.Time domain electromagnetic method is very an effective method to detect the earthinformation. In recent years, not only been applied in engineering exploration, butalso, it play a significant role in the detection of deep underground resources. Timedomain electromagnetic method (TEM) is a method with the principle ofelectromagnetic induction and artificial source detection. It has two kinds ofemission sources, with ungrounded loop (magnetic) and with wire (Electrical). Thedetection depth of electrical source is much larger than magnetic. So it is importantto study the electromagnetic response for the line source. Ground TEM has largeprobing depth, high sensitivity for the abnormal, simple response curve shape andhigh spatial resolution, etc. However, in real detection work of ground TEM, it isnecessary to lay and move launch-receiving device with people. For the detection oflarge area it wastes time and forces, and has low efficiency. Therefore, the study ofthe ground-airborne TEM is necessary.This thesis studies numerical calculation of time-domain ground-airborneelectromagnetic Response about Source of Electrical, the following aspects of theresearch results are achieved:1. According to the electromagnetic field formula of the horizontal electricdipole layered earth surface deduced by M.N.Nabighian, with boundary conditions,the underground electromagnetic field formula of the finite length wire source isdeduced.2. The formula of finite length wire source is applied to the frequency domain,so the Guptasarma numerical linear filtering methods are used for transformationfrom frequency domain to time domain.3. The formula of the electric and magnetic fields of finite length wire source iswith double integral. For the integral of inner, each formula has only a Bessel function. In this paper Bessel function is transformed to hankel transformation withF.N.Kong241point digital filtering method. F.N.Kong241point filtering method isused to calculate hankel transformation. The accuracy meets the electromagneticfield calculation of finite length wire source. For the integral of outer,48-pointGauss integration method is used to calculate the integral of the wire length of thelong grounding wire source, which ensure the calculation accuracy.4. Calculate the underground electric field and contrast with infinitely long wiresource; calculate the vertical response and contrast with uniform half-spaceanalytical solution. The correctness of the formula derivation and the feasibility ofthe numerical method are verified.5. For two infinitely long wire source, in the condition of quasi-staticapproximation, the diffusion equation of electric field is deduced by the passiveMaxwell’s equations. In cartesian coordinate system the earth is partitioned into agrid which forms a five-point difference scheme of the electric field, and ultimatelythe DuFort-Frankel difference equation is deduced. Combined with the stability andboundary conditions, use the finite difference method to calculate the homogeneoushalf-space electromagnetic response, and contrast with the analytical solution toverify the feasibility of the method.6. Calculate the electric field of the uniform half-space containing low resistancesheet, high resistance sheet and low resistance covering layer sheet model, draw thecontour map of the electric field, calculate the electromagnetic response in the air,contrast with the homogeneous half-space respectively, analyze the electromagneticresponse of the different models, and conclude that for time-domain ground-airborneelectromagnetic method magnetic and electric field is sensitive to the low resistivityanomaly; to the high resistivity anomaly magnetic field is not sensitive, but electricfield is sensitive.7. Research on the characteristics of ground-airborne transient electromagneticresponse: Analyze the impact on electromagnetic response of infinitely longgrounded wire source by aircraft flight altitude, and conclude that the change of flightaltitude makes a little impact on ground-airborne time-domain electromagneticmethod; Define the change rate of electromagnetic response relative to the surface fordifferent flight altitude, conclude that it is available to use the method of explainingground electromagnetic data to explain ground-airborne detection system data; Theelectromagnetic response is proportional to emission current value; For anomaly withdifferent resistivity, the transient field is more sensitive to anomaly with lower; Study the selection of the emission source, probing depth and resolution, the responsecharacteristics of dual-source superposition.