三维MCSEM电磁场分解数值滤波方法

浅水域海洋可控源电磁法（MCSEM）具有挑战性的困难之一是如何消除观测数据中的空气波效应，以及来自电磁发射源的直达波影响。本项目首先研究非均匀背景构造（IBC）多域多网格局域拟线性（MDMGLQL）积分方程数值模拟方法，进而分析不同海水深度和三维复杂海底构造下空气波和直达波的影响强度和特征。研究Stratton-Chu型积分及其性质，理论分析、推导并实现电磁场分解数值滤波方法。论证基于本项目从总的观测场分解出来的上行场可以有效消除空气波效应，同时能够压制直达波影响。为了能够处理有限长离散电磁观测实测数据，基于上行场积分解析式，构建数值滤波器。通过分析数值滤波器的频谱特征，确定数值滤波器的计算精度，以及如何选择合适的滤波参数（滤波窗口尺度、采样步长、频率等）。最后，利用典型海洋地电模型模拟数据，以及国内外MCSEM实测数据验证本项目所提方法的稳定性和应用效果。

For shallow water, one challanging problem of marine controlled-source electromagnetic method (MCSEM) is how to remove the effcets of airwave, and direct field which coming from electromagnetic source. Firstly, this project studies a multidomain and multigrid integral equation modeling method with inhomogeneous background conductivity (IBC) using the multiple inhomogeneous domains and multigrid localized quasi-linear (MDMGLQL), then analysies the amplitude and characteristics of airwave and direct wave for the different seawater depth and three dimensitional sea-bottom strutures. Researching Stratton-Chu type integral and its properties, theoretically analyzing,deducing and achieving the digital filter for electromagnetic fields separation, and discussing that one can use electromagnetic upgoing field completed by this project to remove airwave effects, moreover suppress direct wave. Based on above theoretical formula, it's necessary to construct the digital filter which can process practical finite and discrete electromagnetic data. By analyzing frequency spectrum characteristics, we can determine the filter's precision and effectiveness, meanwhile determine reasonable filter parameters such as window size, sampling interval, frequency and so on. Finally, using numerical data for typical marine geological models and oversea practical MCSEM data to test the stability and effect of the method suggested by this project.