冯旭亮^1,2,,
王万银^2,,,
宋立军¹,
袁炳强¹
1. 西安石油大学地球科学与工程学院, 西安 710065
2. 长安大学重磁方法技术研究所, 长安大学地质工程与测绘学院, 西安 710054

基金项目: 陕西省自然科学基础研究计划项目（2018JQ4034）、陕西省教育厅科研计划项目（17JK0617）以及中国地质调查局项目（DD20160227，DD20160227-05）联合资助


详细信息

作者简介: 冯旭亮, 男, 1989年生, 博士, 讲师, 主要从事重、磁勘探方法理论与应用研究及综合地球物理勘探研究及教学工作.E-mail:fxlchd@163.com

通讯作者: 王万银, 男, 1962年生, 博士, 教授, 博士生导师, 主要从事重、磁位场理论及应用研究和教学工作.E-mail:wwy7902@chd.edu.cn

中图分类号: P631

收稿日期:2017-12-28
修回日期:2018-06-27
上线日期:2019-03-05

Gravity inversion for Ⅴ-shaped density interface based on L_p-norm regularization

FENG XuLiang^1,2,,
WANG WanYin^2,,,
SONG LiJun¹,
YUAN BingQiang¹
1. School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an 710065, China
2. Institute of Gravity and Magnetic Technology, College of Geology Engineering and Geomatics, Chang'an University, Xi'an 710054, China


More Information

Corresponding author: WANG WanYin,E-mail:wwy7902@chd.edu.cn

MSC: P631

--> Received Date: 28 December 2017
Revised Date: 27 June 2018
Available Online: 05 March 2019


摘要
摘要:Ⅴ字型密度界面是一类常见的密度界面，如海沟、半地堑以及俯冲带之下的莫霍面，利用重力数据刻画此类密度界面形态对于区域构造研究、油气勘探以及物理海洋学等都具有重要意义.本文首先建立了L_p-范数形式的模型约束函数，并利用正则化原理将其与重力数据误差函数和已知深度约束函数结合形成Ⅴ字型密度界面反演的目标函数，推导了目标函数的梯度表达式，并以非线性共轭梯度法为核心给出了反演流程.二维简单模型试算结果表明p=5时该方法能准确地刻画Ⅴ字型密度界面起伏特征，且亦能准确地应用于二维复杂密度界面和三维界面的反演.最后将反演方法应用于挑战者深渊及邻区的实际资料处理之中，利用研究区海底地形数据和沉积层厚度数据对自由空间重力异常逐层剥离而得到莫霍面引起的重力异常，用本文方法对此重力异常进行反演，结果呈现了板块俯冲作用引起的Ⅴ字型莫霍面起伏特征.
关键词: Ⅴ字型密度界面/
重力异常/
L_p-范数/
非线性反演/
正则化

Abstract:The Ⅴ-shaped density interface is commonly seen such as the ocean trench, half-graben, and the Moho beneath a subduction zone. Delineating the relief of these Ⅴ-shaped density interfaces is of significance in regional tectonic research, physical oceanography and oil and gas exploration.
Among inversion methods of the density interface, the regularization approach, which applies prior information, can guarantee the inversion result to fit the known depth of the interface to be estimated. It can also control the shape of the interface via the model constraint function in the regularization item, making the inversion result agree with the real geologic feature. We have designed a model constraint function in the form of L_p-norm and then integrated it with the gravity data misfit function and the known depth constraint function to establish an objective function for Ⅴ-shaped density interface inversion. Subsequently, we have derived the gradient of the objective function and built the inversion process taking the nonlinear conjugate gradient algorithm as the core.
The effect of our proposed inversion method is related to the value of p. The test results conducted with a two-dimensional simple model show that the method can be used to accurately estimate the Ⅴ-shaped density interface relief when p=5, and the correctness of the proposed method is further confirmed by a two-dimensional Ⅴ-shaped density interface with complex shape. The test results of a three-dimensional Ⅴ-shaped density interface show that our proposed method is also appropriate for three-dimensional inversion. At the end of this article, the inversion method is tested with real gravity data of the Challenger Deep and adjacent regions. The gravity anomalies caused by the Moho were calculated by removing extra gravity effects layer by layer from the free-air gravity anomalies under the constraint of the submarine topography and sedimentary thickness data in this area. Inversion of these gravity anomalies using our proposed method shows that the method is able to delineate the relief of a Ⅴ-shaped Moho under a subduction zone. The estimated depth of the Moho beneath the Challenger Deep ranges 18 km to 20 km, while the depth at the edge of the western Pacific Ocean is 8 km to 12 km, which, to some extent, suggests crustal complexity in the study area. Furthermore, a large inclination of the Pacific subduction slab is inferred from the locations of the maximum of the submarine topography and Moho depth in this area, indicating a relatively slow convergence between the Pacific and Philippine plates.
Key words:Ⅴ-shaped density interface/
Gravity anomaly/
L_p-norm/
Nonlinear inversion/
Regularization



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