大地电磁资料三维傅里叶变换偏移方法及其应用

利用傅里叶变换及内插外推方法对三维大地电磁资料偏移成像问题进行了研究。首先将大地电磁场满足的三维亥姆霍兹方程降维分裂成两个二维响应方程，然后对每一个二维方程进行傅里叶变换，使二维方程变为一维方程，通过大地电磁场垂向方向的导数在地面上所满足的边界条件，确定外推方程中的两个待定系数，从而得到一维外推方程的解。对横向非均匀地电介质，利用分段傅里叶变换方法进行偏移，同时将每一段内电阻率的平均值作为背景值。为了解决纵向介质的不连续问题，取相邻两频点的电阻率值的外推结果进行加权内插。对于横向各段的衔接，采用内插平滑处理。应用该方法对伊朗项目中T01—010测线资料进行了偏移处理，偏移结果除了反映浅层和基底明显的分界面之外，还能较好地反映局部地电异常体引起的异常。

A three-dimensional Fourier transformation migration method of magnetotelluric data and its application

The migration imaging problem of three-dimensional rmgnetotelluric data was studied by Fourier transformation method, inner insert and extrapolate teehnology. First the three-dimensional Hailmuhz equation of magnetotelluric field is split into two 2D equations which could be changed into 1D equation by Fourier transformation method. The two zootomic coefficients of the equation are found out by the derivation of vertical component of electromagnetic field being sufficient the equation and the boundary condition. The resolution of 1D equation can be confirmed. For landscape orientation heterogeneous geoelectricity, migration is conducted by means of fractional Fourier transformation method, taking the averaged value of the subsection resistivity as background value. In order to settle the problem of the longitudinal medium discontinuous, the resistivity of adjacent frequency points is selected to conduct weighted inner insert . The smooth is processed by joining in landscape orientation subsections. The application results of T01-010 line data in Iran show that the interface of shallow and base as well as the abnormity which is caused by local geoelectrical body abnormity is reflected by the migration results.