漳浦外海新生代沉积基底的地震重力综合研究

发布时间：2018-06-01 17:50

本文选题：台湾海峡西南部 + 澎湖—北港隆起　；参考：《地球物理学进展》2017年05期

【摘要】：台湾海峡位于东海陆架盆地和南海东北部的边界,其西南端构造上属于隆起区,分隔厦澎断陷和珠江口盆地,勘探程度较低,以往对该区地质结构的认识仅来源于邻区零星钻井和早期的地震、重磁资料.本文对福建省地震局2015年在漳浦外海部署的一条长约69.7 km的浅层反射地震测线进行了处理,得到了反射波组特征明显、构造现象易于识别的偏移叠加时间剖面.剖面上有一强反射界面可从西端的约300 ms连续追踪到东侧的约600 ms,推测为新生代沉积的底界.偏移速度分析得到的上覆地层P波速度约为2200 m/s,而从海底地震仪记录的折射波中提取的下伏地层P波速度约为5100 m/s.为研究新生代沉积基底的岩性,我们通过融合研究区多种来源的重力数据得到较为准确的剖面重力异常,依据反射地震剖面给出的界面模型进行了重力模拟,结果显示该强反射界面两侧密度差高达0.75 g/cm~3,根据这些特征结合邻区地质露头和钻井资料推测该测线海底至300~700 m深度可能为新生代低固结度的砂岩或泥岩,而其下的沉积基底极有可能为玄武岩等基性火成岩.该结果为研究台湾海峡西南部的地质构造和新生代演化提供了新的地球物理学证据.
[Abstract]:The Taiwan Strait is located at the boundary of the East China Sea shelf basin and the northeast part of the South China Sea. The southwestern end of the Taiwan Strait belongs to the uplift area, separating the Xiapeng fault depression from the Pearl River mouth basin. In the past, the understanding of geological structure in this area was only derived from sporadic drilling, early earthquakes and gravity and magnetic data. In this paper, a shallow reflection seismic line, about 69.7 km long, which was deployed by Fujian Seismological Bureau in the Zhangpu Sea in 2015, has been processed. The migration stacking time profile with obvious characteristics of reflection wave group and easy recognition of structural phenomena has been obtained. There is a strong reflection interface which can be continuously traced from about 300 Ms in the western end to about 600 Ms on the eastern side, which is supposed to be the bottom boundary of the Cenozoic sediments. The velocity of P wave of overlying strata is about 2200 m / s by migration velocity analysis, and the velocity of P wave of underlying strata extracted from refraction wave recorded by submarine seismograph is about 5100 m / s. In order to study the lithology of Cenozoic sedimentary basement, we obtain more accurate profile gravity anomaly by merging gravity data from various sources in the study area. Gravity simulation is carried out according to the interface model given by reflection seismic profile. The results show that the density difference between the two sides of the strong reflection interface is as high as 0.75 g / cm ~ (-3). According to these characteristics and combined with the geological outcrop and drilling data of the adjacent area, it is inferred that the depth from the bottom of the survey line to the depth of 300 ~ 700 m may be a Cenozoic sandstone or mudstone with low consolidation. The underlying sedimentary basement is probably basalt and other basic igneous rocks. The results provide new geophysical evidence for the study of geological structure and Cenozoic evolution in the southwestern Taiwan Strait.
【作者单位】：福建省地震局厦门地震勘测研究中心;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;
【基金】：福建省地震局青年科技基金(Y201407)资助
【分类号】：P736.2

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