宽带高频电磁场数据反演方法研究

Inversion of the wideband and high frequency electromagnetic data

采用非线性最小二乘法结合蒙特卡罗法,实现宽带高频电磁场椭圆极化率数据的精确反演,确定地下层状介质的真实电阻率和介电常数.反演结果表明,对于均匀半空间和二层介质模型,最小二乘法能够很好地实现反演,而对于三层或更多层的介质,首先利用蒙特卡罗法确定拟合初始模型,再进行最小二乘反演,能够避免收敛到局部极小值,提高了反演的稳定性.为了加速正演响应函数的计算和迭代的速度,采用高密度采样的线性滤波算法,大大加快了该精确反演方法的速度.针对如覆盖区地质填图和土壤调查等大面积确定地质体性质的应用,本文还给出了一种近似反演方法(相位矢量图法),能够快速获取视电阻率和视介电常数,不仅可以为应用提供有用的基础信息,而且可作为精确反演方法的初始模型.

To estimate the underground resistivity and permittivity, the nonlinear least-squares inversion method based on Monte-Carlo algorithms is applied in this paper to inverse the wideband high-frequency electromagnetic （WHFEM） polarization ellipse method works well convergence speed, data. The inversion result indicates that the nonlinear least-squares inversion in the half-space or two-layer earth model. In order to reduce instability and increase the Monte-Carlo algorithm is used for multiple-layer model. In the second part, we also adopt the phasor vectorgraph method for fast inversion of apparent resistivity and permittivity which is useful in geology mapping and constructing the initial model for the least-squares inversion.