自动构建大地电磁二维反演的测点中心网格  

Automatic construction of a Site-Centered Grid (SCG) for 2D magnetotelluric inversion

作　　者：陈小斌[1] 赵国泽[1] 

机构地区：[1]中国地震局地质研究所,北京100029

出　　处：《地球物理学报》2009年第6期1564-1572,共9页Chinese Journal of Geophysics

基　　金：中央级公益性科研院所基本科研业务专项(DF-IGCEA-0607-1-6);国家自然科学基金面上项目(40674036)资助

摘　　要：在大地电磁二维反演中,如果网格不均匀或者测点在网格中的位置不恰当,则将出现测点偏离现象,影响反演的精度.此外,由于正演精度和稳定性的需要,反演中网格间距不能差别太大,需要具有一定的光滑性.本文提出了几种自动构建测点中心网格的方法来消除测点偏离现象,并以正则化约束条件来保证网格的光滑程度.本文还提出了一套网格质量检验指标.算例对比研究表明,对于不同的测点集,最佳网格构建的方法可能不相同,但其中"最平模型约束动态配点法"、"最光模型约束动态配点法"拥有最强的适应能力,它们在各种情况下所构建的网格一般同时具备较光滑的网格间距变化和较小的测点偏离程度.此外,采用高质量(光滑性好、测点偏离程度低)网格在一定程度上不仅可提高反演结果的可靠性,还能提高反演的计算效率.本文的方法为获得高质量的大地电磁二维反演网格提供了简单有效的途径.In magnetotelluric （MT） inversion, when the used grid is not uniform or the positions of observation sites in the grid are not appropriate, site shift will occur which can affect the accuracy of inversion. Besides, in order to ensure accuracy and stability of forward modeling, spacing of the inversion grid cannot vary too much, requiring smoothness of some degree. To solve these issues, this paper suggests several methods of automatic constructing a site-centered grid to eliminate site shift and using regularization constraints to control the smoothness of the grid. To realize this object this paper also proposes a set of test indexes for grid quality. Comparison of case calculations indicates that different site sets may require varied methods to construct optimal grids. Among them the ＂optimized dynamic allocation under flattest model constraint＂, and ＂optimized dynamic allocation under smoothest model constraint＂ are most adaptive, by which the constructed grids have fairly smooth grid spacing and smaller site shifts. The comparison also shows that using a grid of high quality （smooth, little site shift） can enhance the reliability of inversion as well as efficiency of inversion calculation. The methods proposed in this paper provide a simple and effective approach to produce a proper grid for 2D MT inversion.

关 键 词：大地电磁 二维反演 测点中心网格 测点偏离 光滑 

分 类 号：P631[天文地球—地质矿产勘探]