Crustal structure of the northwestern sub-basin, South China Sea: Results from a wide-angle seismic experiment
Crustal structure of the northwestern sub-basin, South China Sea: Results from a wide-angle seismic experiment
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DOI：
10.1007/s11430-011-4324-9
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
Zhenli Wu;Jiabiao Li;A. Ruan;Hai Lou;W. Ding;X. Niu;Xibing Li
中科院分区：
文献类型：
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作者：
Zhenli Wu;Jiabiao Li;A. Ruan;Hai Lou;W. Ding;X. Niu;Xibing Li
通过对南海西北次海盆区域及其边界两侧的宽角地震测量线进行反演，模拟了南海西北次海盆区域的地壳结构。测量线延伸超过484公里。总共部署了14台海底地震仪（OBS），间隔30公里，记录总体积为5160 in3的气枪阵列震源。通过对多道地震资料的整合，获得了西北次盆区地壳速度结构。利用射线追踪反演技术对OBS数据进行初步处理和建模。结果表明：陆坡下地壳厚度由21 km减小至11 km，西北次盆地地壳厚度为7.7 km，莫霍线深度由上陆坡下21 km上升至中陆坡下11 km；西北次盆地的地壳结构与东部次盆地的地壳结构相似。这个构造有较厚的一层（沉积层）和较薄的一层。这些特征在与典型洋壳有所不同的东部次盆地中表现得尤为明显。西北次盆地及其边缘的构造几何和速度结构为对称共轭，在大陆边缘裂陷机制上表现为纯剪切模式。西北次盆地北部大陆边缘下地壳下高速层未发现清晰的地震信号，为南海北部大陆边缘西部为非火山地壳的观点提供了新的证据。由于西北次盆地海底扩张期较短，第2层可能经历了不对称的玄武岩岩浆流动，这可能模糊了西北次盆地的磁异常线理。
The crustal structure of the northwestern sub-basin area of the South China Sea was modeled by inverting a wide-angle seismic survey line across the entire region and on both sides of its bounding continental margins. The survey line extended over 484 km. A total of 14 Ocean Bottom Seismometers (OBS) were deployed at intervals of 30 km to record air-gun array sources with a combined volume of 5160 in3. The crustal velocity structure of the northwestern sub-basin area was acquired through the integration of multi-channel seismic data. OBS data were processed and modeled initially using ray tracing inversion techniques. Results indicate that crustal thickness under the continental slope decreases from 21 to 11 km, crustal thickness of the northwestern sub-basin is 7.7 km, and the depth to the Moho ascends from 21 km under the upper continental slope to 11 km under the middle basin. The crust of the northwestern sub-basin is similar to that of the eastern sub-basin in its oceanic crustal structure. This structure has a thicker layer 1 (sedimentary layer) and a thinner layer 2. These characteristics are especially clear in the eastern sub-basin, which differs somewhat from typical oceanic crust. The tectonic geometry and velocity structure of the northwestern sub-basin and its margins comprise a symmetrical conjugate and indicate a pure shear mode with regard to the continental margin rifting mechanism. We did not find clear seismic signals from high velocity layers under the lower crust of the continental margin in the northern part of the northwestern sub-basin, which provides new evidence for the idea that the western part of the northern continental margin of the South China Sea constitutes non-volcanic crust. Because the seafloor spreading period of the northwestern sub-basin was short, layer 2 might have experienced asymmetrical basalt magma flows, which may have blurred the magnetic anomaly lineations of the northwestern sub-basin.