Numerical simulation of the field source for the CSAMT folded line source in a homogeneous half-space
For field surveys using the controlled source audio magnetotelluric(CSAMT)method,it is generally believed that the CSAMT line source is a simplified electric dipole source with a minimal length.However,CSAMT line sources are all arranged in a fol-ded line pattern in field surveys.Based on the previous research results,this study derived the numerical calculation method for the e-lectromagnetic field excited by the folded line source according to the linear superposition principle of electromagnetic fields.Through the calculation of different folded line source models,this study analyzed the influences of the folded line source on the apparent resis-tivity and impedance phase curves in the homogeneous half-space.Model calculations demonstrate that the folded line source signifi-cantly influenced the near and transition zones of the apparent resistivity and impedance phase curves but had no influence on their far zones.The influences on the near and transition zones were primarily caused by the azimuths of folded line segments,and higher azi-muths were associated with more significant influences on the apparent resistivity and impedance phase of survey points.In the case of very low azimuth angles,the folded line source can be approximated as a straight line source for processing,improving the work effi-ciency while fully considering the morphology of the emission source.This study provides theoretical support for the near-field correc-tion of subsequent CSAMT data processing and the CSAMT numerical simulation.
CSAMTnon-linear ground cable sourcehomogeneous half-spacefolded line sourcelinear superposition
万方数据
维普
