地学前缘 ›› 2009, Vol. 16 ›› Issue (4): 252-260.

• 论文 • 上一篇    下一篇

南海东北部及其邻近地区地壳上地幔P波速度结构

  

  1. 中国科学院 地质与地球物理研究所 油气资源研究重点实验室, 北京 100029

  • 出版日期:2009-08-01 发布日期:2009-08-01
  • 作者简介:李志伟(1980—), 男, 博士后, 主要从事地震成像研究。Email: zwli@mail.iggcas.ac.cn
  • 基金资助:

    中国科学院知识创新项目(KZCX3SW2342);国家重点基础研究发展计划“973”项目(2007CB411701);国家高技术研究发展计划“863”项目(2006AA09A1010201)

P wave velocity structure in the crust and upper mantle beneath northeastern South China Sea and surrounding regions.

  1. songKey Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

  • Online:2009-08-01 Published:2009-08-01

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摘要：

利用中国地震台网和ISC台站记录的P波到时数据,采用球坐标系有限差分地震层析成像方法反演了南海东北部及其邻近地区壳幔三维P波速度结构,并分析了不同地质单元的构造差异及其深部特征。结果表明:南海东北部表现出陆架地区的岩石层特性,属于华南大陆向海区的延伸,岩石层厚度较大,现今不存在大规模的地幔热流活动,推测大陆边缘张裂作用仅限于地壳内部而没有延伸进入上地幔,具有非火山型大陆边缘的深部特点。中央海盆附近上地幔P波速度明显降低,与海盆下方地幔热流活动密切相关。不同的速度异常特征表明:华南大陆暨台湾地区属于欧亚大陆的正常地壳或是与菲律宾海板块相互作用产生的增厚型地壳,冲绳海槽则是弧后扩张产生的减薄型地壳。滨海断裂带作为华南大陆高速异常和南海北部高速异常的分界,代表了一定地质时期华南地块和南海地块的拼合边界。断裂附近的上地幔低速异常揭示了闽粤沿海岩浆作用的深层动力机制。吕宋岛弧、马尼拉海沟、东吕宋海槽的速度异常与其所处的特殊构造位置有密切的关系,清晰地反映出岛弧俯冲带的地壳结构差异;台湾南部至吕宋岛弧的上地幔低速异常揭示了两个重要火山链的深部构造特征,北吕宋海脊下方100 km深度的条带状高速异常有可能代表了俯冲下沉的岩石层板片。

关键词: 关键词：南海东北部;P波速度结构;岩石层地幔;层析成像

Abstract:

With the Pwave arrival times from Chinese and ISC stations, we conducted the tomographic inversion for the 3D velocity structure in the crust and mantle beneath the northeastern South China Sea (SCS) and surrounding regions by using spherical finite difference technique. We analyzed the tectonic differences and deep geodynamic characteristics based on the tomographic results, which show high velocity anomalies at the uppermost mantle beneath the northeast SCS, and depict the lithospheric mantle extension from South China continent to marginal sea. Because of the low temperature and thick lithosphere beneath the northeast SCS, it seems no magma intruded from mantle, so we inferred that the rift may only occur in the crust rather than extend to the upper mantle, which shows the nature of nonvolcanic continental margin. The low velocity anomalies at the central subbasin suggest the uplift of hot materials in the mantle. The high velocities at South China continent and Taiwan region, and the low velocities at Okinawa Trough depict the different tectonics of the crust: the former ones belong to the normal crust of Eurasia continent or thickened crust caused by the collision between Philippine Sea Plate and Eurasia Plate, while the latter one belongs to the thinned crust caused by backarc spreading. Between the high velocities of South China continent and northeast SCS, the Binhai fault belt depicts the suture of South China block and SCS block, and the low velocities at upper mantle suggest the deepdriven magma process beneath the marine of South China continent. The velocity anomalies at Luzon, Manila Trench and East Luzon Trench relate to their tectonics natures. The low velocities at the upper mantle from southern Taiwan to northern Luzon depict two volcanic chains: western volcanic chain (WVC) and eastern volcanic chain (EVC). The high velocity belt at north Luzon ridge depicts the subducted continental slab.
Key words: Northeastern South China Sea; P wave velocity structure; lithospheric mantle; seismic tomography

Key words:

关键词：南海东北部;P波速度结构;岩石层地幔;层析成像

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