频率域2维电磁测深资料的RRI反演

本文将大地电磁反演中的RRI方法应用于线源频率测深模型资料的反演中.当背景电导率变化很小时,可用变化前的电场来近似代替变化后的电场,从而在反演方程的推导过程中将有源电磁场中的源项消掉,得到和大地电磁场相同的反演方程,使有源电磁波的反演也可以应用RRI方法.反演过程中所需要的模型资料通过有限元方法得到,该资料不需做近场校正,直接用适合于有源电磁场的RRI方法反演,避免了近场校正带来的误差.数值模型结果证明该方法是可行的.最后,用RRI方法讨论了当源和目标区间存在低阻异常体时只对目标区反演的可行性,对实际工作的解释有一定的指导意义.

RRI inversion of electromagnetic sounding in frequency domain

It is discussed that the RRI method can be applied to electromagnetic inversion scheme due to line source. The source item can be removed during derivating the RRI inversion equations through an approximate condition, that is, the new electric field can be substituted by the old one if the variety of the conductivity is very small, and then the inversion equations become same as that of MT method, which makes it possible to applied the RRI scheme to electromagnetic inversion due to a line source. The theory data can be obtained by 2D finite-element method, and then can be inversed by the RRI scheme directly, which avoid the error caused by near-field correction. The results of digital models show that the RRI scheme is feasible to invert electromagnetic data due to line source without near field correction. At last the feasibility to inverse the data in target area only is discussed when there is a low resistivity abnormalous body between the source and target area.