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一、引言用电磁感应方法研究局部地球电导率结构时经常引用转换函数的概念。转换函数反映了地磁变化的源场与感应场之间的线性关系。由于地磁短周期变化的源场在中低纬度地区是近似均匀的,而其感应场又是由地下感应电流产生,因此转换函数反映了地下电导率分布的某些特证。所以,分析转换函数的空间分布及随频率的变化,可做为研究局部地球电性结构的
I. INTRODUCTION The concept of transfer function is often quoted when studying the local earth conductivity structure using electromagnetic induction method. The transfer function reflects the linear relationship between the source and induced fields of the geomagnetic changes. Since the source field of short-period changes in geomagnetic field is approximately uniform in the middle and low latitudes, and its induced field is induced by the subsurface induced current, the transfer function reflects some special characteristics of the distribution of underground conductivity. Therefore, the analysis of the spatial distribution of the transfer function and the change with frequency can be used to study the local electrical structure of the Earth