大地电磁NLCG与OCCAM二维反演的综合利用

Comprehensive utilization of NLCG and OCCAM in two-dimensional magnetotelluric inversion

大地电磁测深二维正则化反演方法常见的有NLCG(非线性共轭梯度反演)和OCCAM反演等.NLCG反演速度较快,但较依赖初始模型和经验参数输入;OCCAM反演对初始模型和参数依赖较弱,且效果平滑度、与模型的拟合度较好,但是速度慢、计算消耗大;本文采用综合反演法(NLCG2OCCAM,NLCG的反演结果作OCCAM反演的初始模型),旨在结合二者的优势,避免其短板.对典型模型分别进行了TE、TM、TETM三种模式的试算,结果显示综合反演法效果比只进行NLCG反演好,收敛速度上比单独进行OCCAM反演快,从而削弱由于NLCG人为经验参数输入及初始模型带来的影响,同时也能满足速度的需求.通过这些研究,可以对野外大地电磁资料处理与解释提供参考,从而更好地利用其测深资料.

NLCG （nonlinear conjugate gradient inversion ） and OCCAM inversion are the common methods of 2D MT inversion. Both of them have their own advantages and disadvantages, for example, NLCG inversion is faster, but it is more dependent on the initial model and empirical parameters. However, OCCAM inversion is not so dependent on the initial model and parameters, and the effect of smoothness and the fitting of the model are better, but the speed is slow or the calculation is very large. In this paper, it uses the comprehensive inversion method （NLCG2OCCAM, NLCG inversion results for the initial model of OCCAM inversion）, which aims to combine the advantages of the two methods and to avoid the short board. Three kinds of models of TM, TETM and TE are used, the result shows that the effect of the comprehensive inversion method is better than that of the NLCG, and the convergence speed is faster than that of the OCCAM, so as to weaken the impact of NLCG on the input and initial model of the empirical parameters, but also to meet the needs of speed. Through these studies, it can provide a reference for the processing and interpretation of field data in the field, so as to better use of the data from the field.