东沙群岛西南海区海底地震测线OBS2015-1揭示的深部地壳结构

发布时间：2018-06-30 06:26

  本文选题：东沙群岛西南海区 + 海底地震仪(OBS)　； 参考：《热带海洋学报》2017年05期

【摘要】：为深入理解南海北部多道地震测线D80显示的深反射信息,沿此测线布置OBS(15台)地震测线(OBS2015-1),测线长300km,方向NNW—SSE,从水深800m陆坡延伸至3760m深海平原。文章利用Obstool软件进行预处理(位置校正和时间校正等)、震相识别,利用FAST tomography软件进行速度层析成像。速度结果表明,新生代沉积层速度1.6~3.5km·s-1,厚度约2km;中生界速度3.5~5.5km·s-1,平均厚度约3km。在洋陆过渡带处,沉积基底受新生代岩浆活动影响,有较大起伏。在上陆坡处,上地壳存在向上凸起约5km的高速异常,在多道地震剖面中表现为杂乱反射的背斜构造,上覆晚新生代地层也同步形变,推测可能是新生代晚期岩浆侵入造成。地壳厚度由陆坡的23~20km减薄至洋盆的8km。地壳下部存在7.0~7.6km·s-1的高速层,高速层由陆坡的5km左右逐渐递减至海盆的2km左右,因上陆坡和洋陆过渡带晚新生代岩浆活动活跃,作者认为地壳下部高速层是由海底扩张停止后岩浆侵入形成。
[Abstract]:In order to deeply understand the deep reflection information shown by D80 seismic survey line D80 in the northern part of the South China Sea, OBS (15 stations) seismic line (OBS2015-1) is arranged along this line, which is 300km long and NNW-SSE-oriented, extending from 800 m deep slope to 3760 m deep sea plain. In this paper, we use Obstool software to pre-process (position correction and time correction, etc.), identify seismic phase, and use fast tomography software to perform velocity tomography. The velocity results show that the velocity of Cenozoic sedimentary layer 1.6~3.5km s-1 is about 2 km thick, and the Mesozoic velocity of 3.5~5.5km s-1 is about 3 km. In the transitional zone of oceanic land, the sedimentary basement is influenced by Cenozoic magmatic activity and has great fluctuation. At the upper slope, the upper crust has a high speed anomaly of about 5km uplift, which appears in multiple seismic profiles as a chaotic reflection anticline structure, and the late Cenozoic strata are also synchronized deformed, which may be caused by the late Cenozoic magmatic intrusion. The thickness of the crust is reduced from 23~20km in the continental slope to 8 km in the ocean basin. There is a high speed layer of 7.0~7.6km s-1 in the lower crust, and the high speed layer gradually decreases from the 5km of the continental slope to the 2km of the oceanic basin, because of the late Cenozoic magmatic activity in the upper continental slope and the transitional zone of the oceanic continent. The authors believe that the lower crust is formed by magmatic intrusion after the undersea expansion stops.
【作者单位】： 中国科学院边缘海与大洋地质重点实验室(南海海洋研究所);中国科学院大学;广州海洋地质调查局;
【基金】：国家自然科学基金项目(91328205,41376062) 海洋地质保障工程项目(GZH20110205)~~
【分类号】：P736.1
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本文编号：2085306