摘要
三维重力反演被广泛应用于矿产资源勘探和深部密度结构研究,然而传统空间域三维重力场反演方法存在着深度分辨率低、多解性强和计算效率低的问题,影响了地质解释的准确性和可信度.本文针对上述不足,提出基于混合范数正则化约束的频域三维重力场反演方法.首先构建基于深度加权和L1+L2混合范数的模型目标函数.并在反演迭代过程中,采用频域三维重力场正演方法更新模型,将传统空间域三维重力场反演中稠密雅可比矩阵的存储和计算等问题转化为频域正演,大幅度降低内存占用.此外使用高精度高斯型数值积分代替传统快速傅里叶变换(Fast Fourier Transform,FFT)算法中的矩形积分,以保证频域正演方法的计算精度.模型试验表明,相比于传统空间域基于L2范数光滑约束反演方法以及基于L1范数聚焦反演方法,本文反演方法能有效降低三维重力反演的"趋肤效应"和拖尾现象,能恢复出更复杂地质模型,且反演结果更接近真实模型.最后将该方法应用到加拿大魁北克省诺兰达市的Mobrun硫化物矿体三维密度成像,结果显示该矿体深度范围约15~170 m,与前人钻井数据所得深度范围一致,证明了方法的有效性.
3D gravity inversion has been widely used in mineral resources exploration and research on deep density structures.However,traditional 3D gravity inversion methods in spatial domain suffer low depth resolution,severe non-uniqueness and low computational efficiency,which affect the accuracy and reliability of geological interpretation.Aiming at the above problems,this study proposes a 3D gravity inversion method in frequency domain based on a mixed norm regularization constraint.We firstly construct a model objective function based on depth weighting and L1+L2 mixed norm constraints,and apply the frequency domain method of 3D gravity forward modeling to each iteration of an inversion to update the model so that the problems of storing and computing the dense Jacobian matrix in traditional spatial domain inversion methods are transformed into frequency domain forward modeling,which greatly reduces the computational time and memory occupation.To ensure high accuracy of the frequency domain forward method,the high-precision Gaussian numerical integral is used instead of the rectangular integral in traditional Fast Fourier Transform(FFT)algorithm.Two synthetic inversion examples show that the proposed inversion method can effectively reduce the"skin effect"and smearing phenomenon and can recover more complex geological models compared with the traditional spatial domain inversion methods based on L2 norm regularization and L1 norm(focused)regularization.Finally,we apply this method to 3D density imaging of the Mobrun sulfide body in Noranda,Quebec,Canada.The results show that the depth of the sulfide body ranges from~15 to 170 m,consisting with previous borehole data,which proves the effectiveness of the proposed method.
作者
赵广东
王绪本
柳建新
梁生贤
李军
ZHAO GuangDong;WANG XuBen;LIU JianXin;LIANG ShengXian;LI Jun(Key Laboratory of Earth Exploration and Information Technique of Ministry of Education,Chengdu University of Technology,Chengdu 610059,China;College of Geophysics,Chengdu University of Technology,Chengdu 610059,China;Hunan Key Laboratory of Nonferrous Resources and Geological Hazards Exploration,Central South University,Changsha 410083,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2024年第4期1627-1640,共14页
Chinese Journal of Geophysics
基金
国家自然科学基金(42204090,42230311)
四川省自然科学基金(23NSFSC1553)联合资助。
