基于二级近似离散复镜像法的低频电磁格林函数计算  

Calculation of low-frequency electromagnetic Green's functions using two-level approximate discrete complex image method

作　　者：刘云鹤[1] 刘国兴[1] 翁爱华[1] 陈玉玲[1] 贾定宇[1] 廖祥东[1] 

机构地区：[1]吉林大学地球探测科学与技术学院,长春130026

出　　处：《地球物理学报》2011年第4期1114-1121,共8页Chinese Journal of Geophysics

基　　金：国家自然科学基金(40874050)资助

摘　　要：本文讨论了利用二级近似离散复镜像法实现低频格林函数快速、精确的计算.通过数值分析,给出了在低频电磁场计算中该方法近似参数的选取原则.(1)二级近似的积分区间里谱格林函数采样个数N为十倍的近似多项式的个数M;(2)总的积分区间L_2大小约为40/r,r为收发距离;(3)两个积分区间的分界值L_1为总的积分区间大小L_2与第二个积分区间采样数N_1的比值的Q倍;(4)Q的最优值根据谱格林函数拟合相对误差随Q值变化的近似误差曲线与横轴的交点来确定.将该参数选取原则应用到有限长双极源电磁场计算中,计算得到的视电阻率和直接积分结果吻合,且具有更高的精度,表明本文提出的计算方案是可行的.This paper discusses how to apply the two-level approximate discrete complex image method to fast and accurately compute the low frequency Green＇s functions. Through numerical simulation, the approximate parameters in the computation of low frequency electromagnetic field are determined as following： （1） Sampling number N of spectral Green＇s function in the two- approximate integral interval is ten times of the number of approximate polynomial M; （2） The integral interval is about 40/r, where r is the offset; （3） The conjunction value L1 of the two level integral interval is Q times of the ratio of the total size of the integral interval L2 and the sampling number N1 of the second integral interval; （4） The optimal value of Q is determined by the cross point of the spectral Green＇s function approximate error against Q and the horizontal axis. The application of this principle to the calculation of the electromagnetic fields from a finite bipolar source shows that the calculated apparent resistivity agrees with direct integral result very well yet has higher accuracy, showing that the proposed strategy is feasible.

关 键 词：离散复镜像法 电磁法模拟 格林函数 广义函数束法 二级近似 

分 类 号：P631[天文地球—地质矿产勘探]