论文部分内容阅读
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.
The Taiwan Strait is located at the boundary between the East China Sea Shelf Basin and the northeastern part of the South China Sea. The southwestern part of the Taiwan Strait belongs to the uplifted area, separates the Xiapotung Depression and the Pearl River Mouth Basin, and has a low degree of exploration. In the past, the understanding of the geological structure of this area originated only from its neighboring areas Sporadic drilling and early earthquakes, and gravity and magnetic data.In this paper, a seismic reflection line measuring about 69.7 km long deployed by the Seismological Bureau of Fujian Province in the open sea of Zhangpu in 2015 was processed and the characteristics of the reflected wave group were obvious. Phenomenon is easy to identify offset superimposed time profiles.A strong reflection interface in the section can be traced continuously from about 300 ms at the west end to about 600 ms on the east side and is assumed to be the bottom boundary of Cenozoic sedimentation.The overlying The P-wave velocity of the formation is about 2200 m / s, while the P-wave velocity of the underlying formation extracted from the refracted waves recorded by the seabed seismograph is about 5100 m / s. In order to study the lithology of the Cenozoic sedimentary basement, The gravimetric data from various sources in the region are more accurate gravity gravity anomalies, and the gravimetric simulation based on the interface model given by the reflection seismic section shows that the density difference between the two sides of the strong reflection interface reaches as high as 0.75 g / cm According to these characteristics, combining with the geological outcrop and drilling data in the adjacent area, it is speculated that the seabed to the depth of 300 ~ 700 m may be the Cenozoic sandstone or mudstone with low consolidation degree, and the sedimentary base beneath it is most likely to be basalt Basic igneous rocks.The results provide new geophysical evidence for the study of the geological structure and the Mesozoic evolution in the southwestern Taiwan Strait.