何庆禹^1,2,,
郝天珧^1,2,3,4,,,
邢健⁵,
李雪垒^6,7,
李志伟⁷
1. 中国科学院地质与地球物理研究所, 中国科学院油气资源研究重点实验室, 北京 100029
2. 中国科学院大学, 北京 100029
3. 海底科学重点实验室, 自然资源部第二海洋研究所, 杭州 310012
4. 中国科学院地球科学研究院, 北京 100029
5. 国家海洋局东海海洋环境调查勘察中心, 上海 200137
6. 湖南工商大学, 数学与统计学院, 长沙 410205
7. 中国科学院测量与地球物理研究所, 大地测量与地球动力学国家实验室, 武汉 430077

基金项目: 国家自然科学基金（91858212），中科院国际合作伙伴计划课题（132A11KYSB20180020），自然资源部国际合作专项课题（GASI-GEOGE-1）和国家自然科学基金（U1505232）共同资助


详细信息

作者简介: 何庆禹，男，1994年生，在读博士生，主要从事俯冲带地区综合地球物理研究.E-mail：heqingyu@mail.iggcas.ac.cn

通讯作者: 郝天珧，1957年生，中国科学院地质与地球物理研究所研究员，主要从事海陆综合地球物理研究.E-mail：tyhao@mail.iggcas.ac.cn

中图分类号: P312

收稿日期:2020-05-11
修回日期:2020-08-27
上线日期:2021-02-10

Density structure of the crust in the subduction zone of Sumatra region

HE QingYu^1,2,,
HAO TianYao^1,2,3,4,,,
XING Jian⁵,
LI XueLei^6,7,
LI ZhiWei⁷
1. Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
2. University of Chinese Academy of Sciences, Beijing 100029, China
3. Key Laboratory of Submarine Geoscience, Second Institute of Oceanology, Ministry of Natural Resources, Hangzhou 310012, China
4. Institute of Earth Sciences, Chinese Academy of Sciences, Beijing 100029, China
5. East Sea Marine Environmental Investigating & Surveying Center, SOA China, Shanghai 200137, China
6. College of Mathematics and Statistics, Hunan Technology and Business University, Changsha 410205, China
7. National Laboratory of Geodesy and Geodynamics, Institute of Surveying and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China


More Information

Corresponding author: HAO TianYao,E-mail:tyhao@mail.iggcas.ac.cn

MSC: P312

--> Received Date: 11 May 2020
Revised Date: 27 August 2020
Available Online: 10 February 2021


摘要
摘要:俯冲带上覆板片密度特征是认识俯冲及其引发深部岩浆过程的一个窗口.本文以苏门答腊俯冲带空间重力异常数据为基础，在2.5D密度结构剖面约束下，通过3D密度反演，获得了研究区3D密度结构分布.反演结果表明，俯冲板片角度和下倾极限深度均从研究区西北向东南方向逐渐增加；研究区上覆板片下地壳存在低密度异常，主要集中在东南部，分布范围也随深度而增加.分析认为这有可能是俯冲引发的洋壳脱水对上覆板片下地壳侵染所造成.此外，研究区东南部存在的地幔板片撕裂可能是造成该区下地壳低密度异常最为显著的另一个原因.3D密度切片揭示出下地壳密度异常具有沿NE方向延伸迹象，推断应与印澳板块在苏门答腊地区的斜向俯冲作用有关.本文还对研究区的地震分布特征进行了讨论.大部分的浅源地震集中在下倾极限附近，为脆性破裂或摩擦滑移所引发.震源深度大于200 km的地震基本分布在研究区中部和东南部，震源深度从西北向东南方向逐渐加大，这从另一角度为研究区东南部地幔存在板片撕裂的观点提供了佐证.
关键词: 苏门答腊/
俯冲带/
空间重力异常/
密度结构

Abstract:The density characteristics of overriding plate in the subduction zone is a window to understand subduction and the process of its induction of deep magma. This paper, based on the free air gravity anomaly data in the Sumatra subduction zone, restricted by the 2.5D density structure profile, through 3D density inversion, obtains the 3D density structure distribution in the study region. The inversion results show that both the subduction plate angle and downdip extreme depth increase gradually from the northwest to southeast of the study region. The lower crust under the overriding plate of study region is abnormal for low density, which mainly concentrates in the southeast, with the depth increases. The analysis says:the oceanic crust dehydration caused by subduction leads to invasion of lower crust under the overriding plate with a relatively clear direction. Besides, the plate avulsion in the southern mantle of the study region might also be one of the reasons for the lower crust's most remarkable anomaly of low density. The 3D density slice reveals that the density anomaly of the lower crust extends along the NE direction, which should be related to the oblique subduction of India-Australia plate in Sumatra. The characteristics of earthquake distribution in the study area are also discussed. Most of the shallow-focus earthquakes in the research area concentrate near the area of downdip extreme depth, and are caused by brittle fracture or frictional sliding. The earthquakes with over 200km of focal depth are basically distributed in the middle and southeast of the research area, thus showing the trend of gradual increase of focal depth from the northwest to southeast. This provides proof for the viewpoint of plate avulsion in the southern mantle.
Key words:Sumatra/
Subduction zone/
Free air Gravity/
Density structure



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