The Study Of Simulation And Inversion Of1D-Controlled Source Audiofrequency Magnetotellurics Method

Nowadays, As the mid-deep resource prospection is becoming the main trend, itmust also require to improve the geophysical methods, Conventional electricalprospecting has limited depth, generally a few hundred meters. So the electromagneticprospecting has so increasingly extensive foreground.Among it, MT does not needartificial source, can detect the electrical change of rocks within hundreds of kilometersunderground, its field work is convenient,but because of the weak signal, pooranti-interference and time-consuming, its resolution is low.It can only distinguish largesets of geological structure, usually, it is used in general investigation of undergroundelectrical structures.To enhance the strength of signal and suppress the electricalinterference and improve the prospection precision, at this historic moment,ControlledSource Audio-frequency Magnetotellurics method arose.This method has the advantageof great exploration depth, high work efficiency, strong resolution, small terrain effect,high resistance layer shielding effect, etc. During recent years, Controlled SourceAudio-frequency Magnetotelluric method has been widely used in mining, oil and gas,water, coal resources exploration and deep geological structure mapping, and other fields,and is gradually becoming a kind of conventional geophysical techniques.On the study of predecessors, in this article,To horizontal dielectric layer,the formula ofeach component ofelectromagnetic field ofelectric dipole sourcefrequency domain isderived.The Fortran forward programis compiled and calculation is implemented.Asinversion,the writer choose Adaptive Regularization Inversion Algorithm,which is putforward by Chen Xiaobin. Then through the numerical simulation of a variety ofgeo-electrical model,one-dimensional inversion of Controlled Source Audio-frequencyMagnetotelluric method is realized.The forward problem, hypothesis the formation is horizontal layer. To theelectromagnetic field formed by dipole source in homogeneous isotropic media,Maxwell’s equations is transformed to frequency-domain,under the condition ofconforming to thephysical meaning, through mathematical method, converting them intocomponents in the right Angle coordinate system.Finally the forward calculation formulain layered-media is completed. after the deduction of the forward formula,the authorwrite the one-dimensional forward procedure of controlled source audio-frequencyMagnetotelluric method, and realize numerical simulation on typical geo-electric model,Including D, G, H, K, A, KH, HKH and so on, through changing the model parameterssetting, such conditionsas different low-resistance or high-resistance layer resistivity andthickness and different the transceiver,observe the General characteristics of resistivityresponse curve,this is useful to the practical exploration and data processing andinterpretationof Controlled Source audio-frequency magnetotelluric method.The Inverse problem, this paper briefly introduces the advantages and disadvantages ofseveral inversion methods of the electromagnetic exploration and introduces the Adaptive Regularization Inversion method in detail,Including the Regularization Factor, roughnessmatrix, data covariance matrix, etc.As CSAMT data processing, Adaptive regularizationinversion program is wrote,through calculation different1D-theory model,inversionresult is close to the real model, can intuitively give the change tendency of theunderground resistivity by depth, the adaptive regularization inversion algorithm isreliable, lay a solid foundation for the further theoretical research.