基于聚类分析的ModEM三维反演复杂地形网格剖分  

Gridding of complex terrains based on cluster analysis for ModEM 3D inversion

作　　者：胡士晖 闵刚[1] 孙浥钦 陈春江 李春婷 张志豪 HU Shi-Hui;MIN Gang;SUN Yi-Qin;CHEN Chun-Jiang;LI Chun-Ting;ZHANG Zhi-Hao(College of Geophysics,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都理工大学地球物理学院,四川成都610059

出　　处：《物探与化探》2025年第1期148-157,共10页Geophysical and Geochemical Exploration

基　　金：深地国家科技重大专项“深部高温地热能探深评价及开发利用示范”(SQ2024AAA060115);国家自然科学基金重点项目“基于深度学习的青藏高源深部电性结构模型及其动力学特征”(41930112)。

摘　　要：地形因素对大地电磁三维反演结果有显著影响,虽然前人在压制地形影响上已经取得了丰富的研究成果,但在复杂地形(高程变化大)的网格剖分上还存在设计网格复杂与数据高程点校正困难的问题。本文针对主流大地电磁三维反演模块ModEM,提出了一种基于无监督学习的快速带地形网格自动设计剖分新方法,核心内容包括K-means++算法和聚类效果评价,与不考虑地形的均匀分层、等比分层方法相比具有以下优点:①基于聚类的分层方法生成的地形网格具有更高的地形近似度,将地形网格与实际地形之间的平均误差降低了25%;②一定程度上避免了数据高程地形改正的匹配计算;③不仅可用于快速的设计地形网格,其分层特点还可以被参考用于其他建模软件的网格剖分。利用该方法演示了某矿区复杂地形高程数据剖分的全部流程,生成了更能代表实际地形特征的电阻率结构模型,并基于该模型获得了更加精细的三维反演结果。理论和实际应用说明该方法极大地提高了网格剖分的地形适应性,对于压制大地电磁三维反演地形影响具有重要的意义。The topographic factor significantly influences the 3D inversion results of magnetotelluric data.Despite extensive research results previously obtained in suppressing topographic effects,the gridding of complex terrains(with significant elevation changes)is still challenged by grid design complexity and difficulty in correcting data elevation points.Based on the mainstream 3D inversion module ModEM for magnetotelluric data,this study proposed a novel method for rapid automatic grid design and partitioning of terrains based on unsupervised learning,primarily involving the K-means++algorithm and the assessment of clustering effects.Compared to the uniform and equal proportion-based hierarchical methods ignoring the topographic factor,the proposed method shows the following advantages:(1)The terrain grid generated by the clustering-based hierarchical method manifested higher terrain approximation,reducing the average error between the terrain grid and the actual terrain by 25%;(2)The matching calculation for terrain correction based on the digital elevation model was somewhat avoided;(3)The rapid design of terrain grids can be achieved,and the hierarchical characteristics can be referenced for gridding in other modeling software.The proposed method was employed to demonstrate the whole process of partitioning the elevation data of a complex terrain in a mining area,generating a resistivity structure model more representative of the actual terrain characteristics.Based on this model,finer-scale 3D inversion results were obtained.Theoretical and practical applications illustrate that the proposed method can significantly improve the topographic adaptability of gridding,holding critical significance for suppressing topographic effects on the 3D inversion of magnetotelluric data.

关 键 词：音频大地电磁法 MODEM 地形网格剖分 K-means++ 

分 类 号：P631[天文地球—地质矿产勘探]