Adaptive unstructured grid finite element simulation of two-dimensional magnetotelluric fields for arbitrary surface and seafloor topography
Adaptive unstructured grid finite element simulation of two-dimensional magnetotelluric fields for arbitrary surface and seafloor topography
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DOI：
10.1111/j.1365-246x.2007.03481.x
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发表时间：
2007-10-01
影响因子：
2.8
通讯作者：
Spitzer, Klaus
中科院分区：
文献类型：
--
作者：
Franke, Antje;Boerner, Ralph-Uwe;Spitzer, Klaus
提出了一种自适应非结构三角形网格有限元方法来有效地模拟二维导电结构中的平面波扩散电磁场。不规则网格的最大优点是它可以结合包括表面和海底地形在内的任意几何形状。使用后验误差估计器的自适应网格加密策略产生了最有效的数值解，因为网格只在需要的地方被加密。我们通过与解析解和先前发表的数值模拟的比较，证明了该方法的稳健性。最大误差可以系统地减小到例如视电阻率的0.8%和相位的0.2度。对E极空气层厚度的另一项精度研究建议根据地球内部的横向电导率对比保持最小厚度。此外，通过处理两个海洋大地电磁应用，我们指出了我们的模拟技术的新的质量和灵活性。在第一种情况下，我们讨论了与合成正弦海底模型相关的地形效应，在第二种情况下，我们使用来自南纬17度的东太平洋隆起的真实水深数据，展示了一个接近现实的场景。
We present an adaptive unstructured triangular grid finite element approach for effectively simulating plane-wave diffusive electromagnetic fields in 2-D conductivity structures.The most striking advantage of irregular grids is their potential to incorporate arbitrary geometries including surface and seafloor topography. Adaptive mesh refinement strategies using an a posteriori error estimator yield most efficient numerical solutions since meshes are only refined where required.We demonstrate the robustness of this approach by comparison with analytical solutions and previously published numerical simulations. Maximum errors may systematically be reduced to, for example, 0.8 per cent for the apparent resistivity and 0.2 degrees in the phase.An additional accuracy study of the thickness of the air layer in E-polarization suggests to keep a minimum thickness depending on lateral conductivity contrasts within the earth.Furthermore, we point out the new quality and flexibility of our simulation technique by addressing two marine magnetotelluric applications. In the first case, we discuss topographic effects associated with a synthetic sinusoidal sea bottom model and in the second case, we show a close-to-reality scenario using real bathymetry data from the East Pacific Rise at 17 degrees S.