基于非均匀网格有限差分法的大地电磁静位移模拟

Modeling of Magnetotelluric Static Shift Based on Non-Uniform Meshes Finite Difference Method

摘要: 在大地电磁勘探中，视电阻率曲线总会存在一些静态现象，而静态问题又一直是电磁测深领域一个棘手的问题，它直接影响到电磁测量结果的解释，能否正确识别静态是实际勘探工作能否顺利进行的一个关键，同时也关系到测深工作的成败。为了计算二维静位移地电模型的大地电磁响应，本文采用非均匀网格有限差分法进行了数值模拟。从电磁场满足的微分方程出发，利用非均匀网格有限差分法导出了二维大地电磁正演计算的线性方程组。通过对浅部不均匀体模型的模拟计算，得到了大地电磁的静位移响应规律，同时也验证了非均匀网格有限差分正演算法的准确性。

Abstract: Because of the existence of shallow inhomogeneous bodies, static shift occurs in magnetotelluric sounding curves, which makes the interpretation of magnetotelluric data very difficult, or even impossible. It is very important to identify static shift in the interpretation of magnetotelluric data. In this paper, in order to compute the two-dimensional magnetotelluric responses of static shift model, non-uniform grids finite difference method was adopted for numerical results. From the electric field and magnetic field based on the differential equation, the linear equation for magnetotelluric numerical modeling was derived by non-uniform meshes finite difference method. By the numerical simulation for the geo-electric model with shallow inhomogeneous body, the character of static shift can be obtained and the magnetotelluric responses computed by non-uniform girds finite difference method are effective.