Crustal structure and fracture zone in the Central Basin of the South China Sea from wide angle seismic experiments using OBS
Crustal structure and fracture zone in the Central Basin of the South China Sea from wide angle seismic experiments using OBS
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利用OBS广角地震实验研究南海中部盆地地壳结构和断裂带
DOI：
10.1016/j.tecto.2016.09.022
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发表时间：
2016-10-12
期刊：
影响因子：
2.9
通讯作者：
Wang, Xinyang
中科院分区：
文献类型：
--
作者：
Ruan, Aiguo;Wei, Xiaodong;Wang, Xinyang
本文介绍了两条东西向宽角地震剖面（OBS 2013-ZN、OBS 2014-ZN），它们穿过南海东部次海盆和西南次海盆的边界（中南断裂带）。我们处理数据，并使用二维射线追踪，以确定洋壳厚度，速度结构和莫霍面深度变化有关的断裂带。模拟的速度模式表明，南海洋盆具有典型的洋壳，其上覆盖着1- 2km厚的沉积层，速度为2.0- 3.5km/s。地壳厚度为5-8公里，其中大洋2层厚度为1.8-3公里，向下速度从4.3公里/秒增加到6.4公里/秒，大洋3层厚度为3-5公里，向下速度从6.4公里/秒增加到7.0公里/秒。大洋盆地的莫霍面深度约在海床以下6-7公里。莫霍面有一个明显的隆起带，其低速为7.6 km/s，其位置对应于大洋第2层的低速带。研究结果表明，两个剖面莫霍面隆起部分的连接是一条NW -SE向的断裂带（宽40-60 km），而不是一条南北向的“中南断裂”。研究区的北西-南东向中南转换断裂带与南海演化末期的开海方向一致。这条大型转换断裂带连接并错开了盆地东部和西南部的扩张中心。(C)2016作者由爱思唯尔公司出版
We present two E-W trending wide-angle seismic profiles (OBS2013-ZN, OBS2014-ZN), which cross the boundary (Zhongnan fault zone) between the east sub-basin and the southwest sub-basin of the South China Sea (SCS). We processed the data and used 2D ray-tracing to determine the oceanic crust thickness, velocity structures and Moho depth variations related to the fault zone. The simulated velocity models show that the oceanic basin of the SCS has a typical oceanic crust covered by a 1-2 km thick sediment layer with a velocity of 2.0-3.5 km/s. The crust has a thickness of 5-8 km, of which the oceanic layer 2 is 1.8-3 km thick, with velocity increasing downward from 4.3 km/s to 6.4 km/s, and the oceanic layer 3 is 3-5 km thick, with velocity increasing downward from 6.4 km/s-7.0 km/s. The Moho depth in the oceanic basin is approximately 6-7 km below seabed. The Moho discontinuity has a prominent upheaval zone with a low velocity of 7.6 km/s, whose location corresponds to the low velocity zone in oceanic layer 2. Our results suggest the presence of a NW -SE-trending fracture zone (40-60 km wide) rather than a major "Zhongnan fault" oriented N-S by connecting the upheaval portions of the Moho in the two profiles. The NW-SE orientation Zhongnan transform fault zone in our study area is consistent with the direction of opening of the South China Sea in the last stage of its evolution. This large transform fault zone connected and offset the spreading centers of the east and southwest sub-basin. (C) 2016 The Authors. Published by Elsevier B.V.