自适应有限元海洋大地电磁场二维正演模拟

Adaptive finite element forward modeling for two-dimensional marine magnetotelluric fields

自适应有限元海洋大地电磁场二维正演算法是在完全非结构三角单元网格上实现的,这种网格能够真实地拟合地形起伏、倾斜界面等复杂地质构造,并且该方法能够自动细化网格并在不显著增加计算时间的条件下提供可靠的计算结果。通过模拟二维地电模型大地电磁场响应,并与规则矩形网格有限元数值解进行比较,验证了算法和程序的正确性和精度。最后,计算了两个海底起伏地形模型的大地电磁场响应,且与陆地模型的大地电磁场进行对比,讨论了海底地形起伏对海洋大地电磁场响应的影响。

In this paper,we present an unstructured and adaptive finite element(FE)algorithm for 2D magnetotelluric forward modeling.The unstructured triangular grids can exactly accommodate complex topography and dipping interfaces.Adaptive finite element method can automatically improve mesh design and offer reliable numerical results without significantly increasing the computing time. We compute the magnetotelluric response of a 2Dmodel using the presented FE algorithm,and compare the numerical results to those obtained by the previous FE code with the use of structured rectangular grids.It is verified that the presented algorithm and code are correct and accurate.We finally investigate effects of bathymetry on magnetotelluric responses.