球坐标系密度界面反演方法及在华南大陆的应用  

Density interface inversion method in spherical coordinates and its application in the South China mainland

作　　者：王祥 郭良辉[1] WANG Xiang;GUO Liang-Hui(School of Geophysics and Information Technology,China University of Geosciences(Beijing),Beijing 100083,China;Kunming Natural Resources Comprehensive Survey Center of China Geological Survey,Kunming 650000,China)

机构地区：[1]中国地质大学(北京)地球物理与信息技术学院,北京100083 [2]中国地质调查局昆明自然资源综合调查中心,云南昆明650000

出　　处：《物探与化探》2020年第5期1161-1171,共11页Geophysical and Geochemical Exploration

基　　金：国家自然科学基金面上项目(41774098)。

摘　　要：密度界面反演方法在油气勘探、推断区域构造、获取地壳结晶基底面、莫霍面起伏形态等方面具有重要意义。现有的密度界面反演方法大多基于笛卡尔坐标系统,当涉及到大区域乃至全球尺度的密度界面反演时,地球曲率的影响将不可忽视,需考虑基于球坐标系Tesseroid模型的密度界面反演方法。然而,受计算精度和效率制约,已有的基于Tesseroid模型的密度界面反演方法并不能很好地适用于地表重力观测数据的反演计算。笔者基于前人研究,给出了一种适用于地表观测数据的球坐标系密度界面反演方法。该方法首先将常规的球坐标系高斯—勒让德重力积分公式进行简化,提高了重力正演计算效率。随后,引入并改进了前人的自适应剖分方案,提高了重力正演计算精度。在此基础上,采用Cordell迭代优化算法,得到了适用于地表观测数据的球坐标系密度界面反演方法。通过模型数据试验,对本文球坐标系密度界面反演方法进行了验证。结果表明,笔者对高斯—勒让德积分公式加以改进和引入改进的自适应剖分方案后,很好地克服了计算精度和效率对地表观测重力计算的掣肘,并且,基于球坐标系的密度界面反演结果优于基于笛卡尔坐标系的密度界面反演结果。在华南大陆实际数据试验中,利用文中方法得到的华南大陆的莫霍面深度与前人得到的莫霍面深度具有较高的吻合度,莫霍面自西向东逐渐抬升,西部抬升剧烈,东部抬升平缓,沿武陵山—贵桂交界一带呈现明显的NNE向莫霍面梯级带,验证了文中方法的科学有效性。The density interface inversion method has been playing an important role in the oil and gas exploration,regional structure inference studies as well as crustal crystal basement surface and Moho undulations researches.Most of the density interface inversion methods are generally based on the Cartesian coordinate system.When large regional or even global scale data are dealt with,the influence of earth curvature cannot be ignored,and the density interface inversion method based on Tesseroid model of spherical coordinate system needs to be considered.However,due to the limitations of calculation accuracy and efficiency,the existing density interface inversion method based on Tesseroid cannot be well applicable to the surface gravity observation data.In this paper,on the basis of previous studies,a density interface inversion method of spherical coordinate system suitable for surface observation data is proposed.Firstly,the gravity Gauss-Legendre integral formula in the spherical coordinate system is simplified to improve the forward calculation efficiency.Then,an optimized adaptive subdivision algorithm is introduced to enhance the calculation accuracy.According to the previous forward calculation and by using Cordell iterative optimization algorithm,the authors propose a density interface inversion method for the surface observation data in the spherical coordinate system.The proposed inversion method in this paper can be verified through the synthetic data test.The inversion results show that the proposed method can overcome the limitation of calculating precision and efficiency of the surface observation data.In addition,the inversion results based on spherical coordinate system are better than those based on cartesian coordinate system.Finally,tests on real data from South China mainland verify the feasibility of the presented methods.The results show that Moho depth rises gradually from the west to the east,with the western part uplifting dramatically and the eastern part uplifting gently.Between Wuling Mounta

关 键 词：重力 球坐标系 密度界面反演 Tesseroid 华南大陆 

分 类 号：P631[天文地球—地质矿产勘探]