直流激电测深二维反演的若干问题研究

目前,激电数据的二维反演主要针对高密度激电数据,而对于常规的激电测深则很少涉及.据此,针对常规激电测深二维反演所涉及到的一些技术难点进行探讨.在正演过程中,根据实测数据实现有限元网格自动剖分,并采用双网格系统,用相邻节点电导率双线性连续进行有限元模拟,并对模拟的误差进行校正.在反演过程中,利用互换原理和Broyden的方法计算偏导数矩阵;采用与奇异值分解算法精度相当的共轭梯度算法求解偏导数矩阵方程.最后通过对模拟数据和实测数据进行反演试算,验证本计算方法是可行的.

SOME PROBLEMS CONCERNING 2D INVERSION OF DIRECT CURRENT IP SOUNDING DATA

At present,the researches on 2D inversion of IP data mainly aim at the HD(high density) IP data,which is mainly due to the equivalent distances between neighboring poles during data collection.Under such a condition,the division of finite element grid is convenient and the forward and inverse operation is easy.In forward operation,the finite element grid is automatically divided according to the practical data,and dual-grid system is used.The finite element modeling with linear variation of conductivity within each block is done,and the error of modeling result can be modified.In inversion,the partial derivatives of the apparent resistivity with respect to model resistivity are calculated by means of the relationship between the source and receiver locations and Broyden's method.And it is solved by using the conjugate gradient method,in which the calculation precision is almost the same as that in the SVD method.Through inversing the modeling data and observed data,it is shown that the algorithms of this paper are workable.