可控源音频大地电磁数据的反演方法

从反演方程、构造目标函数和求解三方面对用于可控源音频大地电磁法(CSAMT)的实用反演方法中的四种进行了描述．水平层状地层CSAMT法资料的直接反演法首次尝试了一维空间的全资料CSAMT反演，效果较好，但该方法尚难应用于2D、3D复杂介质中；奥克姆反演方法既考虑了横向的光滑函数，又考虑了纵向的光滑函数，得到比较光滑的横向、纵向变化的背景电性结果，但有可能把一些小构造光滑掉．快速松驰反演算法和共轭梯度算法由于计算速度快，占内存少而被用于三维反演中，二者相比，快速松驰算法在求解雅可比矩阵时只做一次正演计算，在更新模型时解小型方程组，所以在速度上更胜一筹．在后三种算法中，由于复杂电性结构无解析解，正演计算都采用数值计算．数值计算的可靠性、速度影响着反演算法的有效性，这方面的研究也将是2D、3D复杂电性结构反演的研究方向之一.

Inversion method of controlled source audio-frequency magnetotelluric data

This paper is a review on inversion method of controlled source audio-frequency magnetotellurics data. For a horizontally layered earth it was the first time people get the better result from the direct inversion with full wave data than with single plane wave data only. But the method is difficult to apply to 2D and 3D earth medium with complicated electric structures. For the 2D complex earth medium with lateral and vertical variation, Occam inversion method not only consider the lateral smooth function but also the vertical smooth function, the good result of smoothed lateral and vertical electric property can be obtained,but some small features may be smoothed out. Rapid relaxation and conjugate gradients inversion algorithm have advantages of calculation time and computer memory saving. they have frequently been used in 3D inversion. Rapid relaxation method is better in saving calculation time, because it need only solve small set of equations in updating model and only do one forward solution in each inverse iteration, at the same time, the Jacoby matrix is obtained. Because of no analytical solution for complex earth, the numerical calculation is needed in forward solution for the later three methods. The reliability and calculation velocity of forward modeling, affect the efficiency of inversion method, so this is one of research direction of future study in inversion method for 2D,3D complex earth.