李小林^1,2,,
张冬丽^1,2,,,
张培震^1,2,
李志刚^1,2,
胡立天^1,2,
郑文俊^1,2
1. 中山大学地球科学与工程学院, 广东省地球动力作用与地质灾害重点实验室, 广州 510275
2. 南方海洋科学与工程广东省实验室(珠海), 珠海 519082

基金项目: 广东省引进人才创新团队项目（2016ZT06N331），国家自然科学基金（41774049，41674051，41590861）联合资助


详细信息

作者简介: 李小林, 女, 1994年生, 硕士研究生, 从事地球物理方向的研究.E-mail:lixl26@mail2.sysu.edu.cn

通讯作者: 张冬丽, 女, 1974年生, 副教授, 从事地震工程、地震灾害机理与强地震动理论研究.E-mail:zhangdongli@mail.sysu.edu.cn

中图分类号: P315;P738

收稿日期:2019-06-13
修回日期:2019-11-02
上线日期:2020-04-05

Three-dimensional crustal structure in the northeastern South China Sea revealed by multi-source geophysical exploration data

LI XiaoLin^1,2,,
ZHANG DongLi^1,2,,,
ZHANG PeiZhen^1,2,
LI ZhiGang^1,2,
HU LiTian^1,2,
ZHENG WenJun^1,2
1. Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
2. Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai), Zhuhai 519082, China


More Information

Corresponding author: ZHANG DongLi,E-mail:zhangdongli@mail.sysu.edu.cn

MSC: P315;P738

--> Received Date: 13 June 2019
Revised Date: 02 November 2019
Available Online: 05 April 2020


摘要
摘要:南海东北部洋陆转换带及其邻区复杂的地壳结构一直是南海岩石圈结构研究和深水油气勘探的热点.本研究基于覆盖南海东北部的119条地球物理探测数据（包括二维地震和OBS/OBH/ESP等剖面），采用已有OBS数据拟合的时-深关系进行转换，提取主要沉积地层界面和Moho面深度信息；参考区域深钻资料，利用离散平滑与克里金插值法对研究区的数据稀疏区进行插值，在此基础上建立了南海东北部三维地壳结构模型.结果显示：南海东北部的地壳拉伸减薄具有空间差异性.平面上，可以分为地壳轻微、中等和强烈减薄区（拉伸系数分别小于1.5、1.5~2.5之间和大于2.5）；Moho面深度向SW向变浅，洋陆转换带宽度由东部的50 km变窄至西部的20 km；北部陆架区发育一系列NE走向的断陷，推测主要受到滨海断裂带的控制，南部陆坡深水区部分凹陷发育巨厚沉积层，可能是由于深水区大型正断层活动和南海扩张过程中陆壳向海掀斜的共同作用.垂向上，Moho面深度与沉积层底界表现为镜像关系，上地壳拉伸系数基本都大于下地壳；且东沙隆起及其邻区的下地壳下部发育高速层，其厚度以近东西向为轴向南北方向变薄.研究揭示的南海东北部三维地壳结构，特别是Moho面结构特征，是认识其深部动力过程和构造活动的重要依据，可为探讨南海洋盆的扩张和演化提供参考.
关键词: 南海东北部/
洋陆转换带/
时深转换/
三维地壳结构/
地壳减薄

Abstract:The complexity of crustal structure of the ocean-continental transition (OCT) and its adjacent areas in the northeastern South China Sea (SCS) have been always a research hot-spot in lithospheric structure and deep-water oil and gas explorations. Using 119 geophysical data (including 2D seismic and OBS/OBH/ESP profiles, etc), borehole drilling data, discrete smoothing and Kriging interpolation methods in sparse data area, we show a spatial variability 3D crustal structure framework of crustal stretching and thinning in northeastern South China Sea. This result is independent of time and depth, demonstrated by both the sedimentary layer and Moho reflections. The spatial variability exhibit to be the slight, modest and intensive thinning in plane view (the stretching factor are less than 1.5, between 1.5 and 2.5, and greater than 2.5 respectively). Moho depth is shallowed towards SW, and the OCT width is narrowed from 50 km in the east to 20 km in the west. Aside from that, a series of depressions with NE-orientation on the northern continental shelf area are supposed controlled by the Littoral Fault Zone. The huge-thick sediment layers in the deep-water depressions, in addition, indicate this faulting activity and tip tilting towards the sea during the spreading of the South China Sea. In vertical, The Moho depth and the bottom boundary of the sedimentary strata show a mirroring reflection, and the upper crustal stretching factor is substantially larger than that of the lower crust. Moreover, a high-velocity layer (HVL) under the lower crust of the Dongsha uplift and its adjacent areas tends to align along E-W axis and the thickness was thinned in the N-S direction. The 3D crustal architecture in northeastern SCS revealed by the bottom boundary of the sedimentary strata inversion, especially the Moho profile morphology, will enhance our understanding of the dynamic process and tectonic activity in South China Sea, and provide additional constraints for the SCS oceanic basin spreading.
Key words:Northeastern South China Sea/
Ocean-continental transition/
Time-depth conversion/
Three-dimensional crustal structure/
Crust thinning



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