三维重力、重力梯度和大地电磁数据的平滑聚焦结构约束联合反演  

Three-dimensional cross-gradient joint inversion of gravity,gravity gradient and magnetotelluric data based on smooth-focusing regularization method

作　　者：何浩源 李桐林[1] 张镕哲 朱威[2] HE HaoYuan;LI TongLin;ZHANG RongZhe;ZHU Wei(College of Geo-exploration Sciences and Technology,Jilin University,Changchun 130012,China;Key Laboratory of Geophysical Electromagnetic Probing Technologies of Ministry of Natural Resources,Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang 065000,China)

机构地区：[1]吉林大学地球探测科学与技术学院,长春130012 [2]中国地质科学院地球物理地球化学勘查研究所自然资源部地球物理电磁法探测技术重点实验室,廊坊065000

出　　处：《地球物理学报》2022年第5期1822-1838,共17页Chinese Journal of Geophysics

基　　金：自然资源部地球物理电磁法探测技术重点实验室开放课题基金(KLGEPT201909);国家重点研发计划(2017YFC0601606);中国博士后科学基金特别资助(站前)项目(2020TQ0114);中国博士后科学基金资助项目(2020M681036)联合资助.

摘　　要：多种地球物理数据联合反演解释能够显著提高勘探分辨率,近年来,基于交叉梯度结构约束的联合反演得到了广泛研究.该方法有效克服了单一方法反演易受多解性影响和不同方法反演结果结构不一致等问题,已成为目前最流行的联合反演技术之一.传统的重力和大地电磁联合反演常因重力纵向分辨能力弱,导致密度模型可靠性较低,进而使联合反演结果有失准确.因此,本文在重力数据的基础上加入了包含更多高频信息的重力梯度数据,以更好地恢复出地下密度结构,进而提高联合反演的分辨率.同时,本文又提出了一种平滑聚焦的正则化方法,并将其应用于重力、重力梯度和大地电磁数据的三维联合反演中.平滑聚焦正则化法是平滑和聚焦正则化方法的结合,它既能保证异常体轮廓在大尺度上的光滑性,减少局部假异常,又能捕捉反演解的小尺度细节,增强反演结果的稀疏性,得到尖锐的异常体边界.通过设置聚焦强度阈值避免了聚焦和平滑聚焦反演中存在的过度聚焦问题.此外,为了减弱交叉梯度结构约束对反演模型向真实模型迭代的限制,本文还提出了一种间断式联合的交叉梯度联合反演新策略,令单独反演和联合反演交替进行.模型试算结果表明:重力梯度信息的加入有效提高了密度模型的可靠性,从而改善了联合反演的效果;平滑聚焦正则化法使大地电磁的反演结果更加准确,提高了电阻率模型的可靠性;间断式联合的反演策略既保证了交叉梯度法的结构相似约束,又能让迭代模型响应向观测数据充分拟合,使联合反演结果更还原真实模型.The joint inversion interpretation of multiple geophysical data can significantly improve the exploration resolution.In recent years,joint inversion based on cross-gradient structure constraints has been widely studied.This method effectively overcomes the problem that single inversion is easily affected by the multiplicity of solutions and the model structure of inversion results by different method are inconsistent,which has become one of the most popular joint inversion techniques.Due to the weak vertical resolution of gravity method,the traditional joint inversion of gravity and magnetotelluric usually lack of a reliable density model,which leads to poor accuracy of results.Therefore,the gravity gradient data with more high-frequency information is added in this paper,which can restore the underground density structure better and improve the resolution of cross-gradient joint inversion.At the same time,a smooth-focusing regularization method is proposed and applied to the joint inversion of gravity,gravity gradient and magnetotelluric data.Smooth-focusing regularization is a combination of smooth regularization and focusing regularization.It can not only ensure the smoothness of abnormal body contour on a large scale,reducing the local false anomalies,but also capture the small-scale details of the inversion solution,enhancing the sparsity of results and obtaining sharp anomaly boundaries.We avoid the over-focusing problem in focusing or smooth-focusing inversion by setting the focusing intensity threshold.In addition,in order to reduce the restriction of cross-gradient structure constraint on the iteration from inversion model to real model,a new discontinuous joint strategy for cross-gradient joint inversion is proposed in this paper,which makes the single inversion and joint inversion alternate.The model test results show that:the reliability of density model is effectively improved by adding gravity gradient information,and the effect of joint inversion is improved;the smooth-focusing regularization metho

关 键 词：重力和重力梯度法 大地电磁法 交叉梯度联合反演 平滑聚焦正则化 聚焦强度阈值 间断式联合策略 

分 类 号：P631[天文地球—地质矿产勘探]