中文摘要：

系统分析大地电磁三维交错采样有限差分算法的基础上,根据可控源音频大地电磁场特征,采用将总场分解为一次场和二次场计算,一次场利用快速汉克尔变换,二次场利用数值模拟的思路.从CSAMT满足的麦克斯韦方程组积分形式出发,利用交错采样有限差分算法推导了电场和磁场的离散关系式,提出了简洁的边界条件和合理的剖分方案,所实现的CSAMT三维正演算法具有迭代速度快、收敛稳定、计算精度高等特点.通过均匀半空间和三维低阻体两个理论模型的计算结果检验了算法的正确性和计算精度,为CSAMT三维反演奠定了基础.

英文摘要：

On the basis of systems analysis the magnetotelluric 3-D modeling using staggered-grid finite difference method, the general field was decompounded into two parts with the characteristic of CSAMT field, one was the background field calculated by Fast Hankel Transform, and the other was the secondary field elicited by numerical modeling. The discrete equations of electric field and magnetic field are derived from integral format of Maxwell＇s equation using staggered-grid finite difference method. More explicit boundary conditions and reasonable dissect method were also introduced. The result shows that, the fast algorithm has high-precision and stability convergence to CSAMT 3D forward modeling. The validity and precision have been proved by a uniformity half space model and a 3 D low resistivity prism model. The efficient algorithm has setup basis for future research of 3-D CSAMT inversion.