网格剖分及边界对MT Occam反演的影响研究

The study of effect of mesh generation and boundary on MT Occam inversion

在大地电磁有限元模拟计算中网格剖分及边界放置是否得当,影响着最终的反演结果。基于Occam反演法从网格剖分及边界方面,设计不同模型,讨论不同网格对反演精度的影响。研究表明,对于二维介质体,只要将网格边界置于适当倍数趋肤深度的距离处,便可忽略截断边界的影响,无需放置在无穷远。在同一频段及不均匀剖分的前提下,粗细网格均可获得良好的反演结果。细网格的反演精度高于粗网格,但未能很好地圈定异常体的边界。粗网格剖分下,MT Occam法对低阻异常体反演效果较好,而对高阻异常体效果较差。

The grid subdivision is reasonable or not and the boundary select appropriately of MT modeling using finite element method have influence on the inversion results.Based on Occam inversion method,using different models from grid subdivision and boundary settings,discussed their effect to the inversion results.The result show that mesh boundary are not necessary to place at infinity only in the appropriate multiple skin depth distance can ignore the influence of the truncation boundary on two-dimensional media.At the premise of same frequency band and non-uniform subdivision,good inversion results can be obtained from both fine mesh and coarse mesh.The inversion accuracy of fine grid better than that of the coarse grid,but not good at delineating the boundary of the abnormal body.The MT Occam results of coarse grid for the abnormal body of low resistance is better,however for abnormal body of high resistance,the results is worse.