南海北部海陆联合深地震探测及其地质学意义

Joint onshore-offshore deep seismic prospect in the northern South China Sea and its geological implication

南海北部海陆地震联测经历了旧气枪震源的初始试验、大容量气枪的引进与改造、陆上台站和海底地震仪联合接收等3个阶段,填补了海陆过渡带深部结构的研究空白,其结果显示滨海断裂带在速度结构上表现为低速特征,并揭示了南海北部陆缘地震带的深部发震构造与地壳内部低速结构和交叉断裂的耦合作用存在紧密联系。西沙和南沙海陆联测为北部联测的进一步工作,可以构建穿越南海北部陆缘、西沙地块到南沙地块等陆缘的超长地壳结构剖面,对我们揭示南沙地块内部微块体结构、南沙地块及其邻区的深部速度结构以及南沙地块与周边海盆、陆块间过渡带的综合地质地球物理结构,了解南沙地块现今的构造状态与构造变迁历史,解译南沙地块裂离演变过程等具有重要意义。

The onshore-offshore seismic exploration in the northern South China Sea has experienced three stages： initial test using old air-gun source,import and improvement of large volume air-gun,and joint receive air-gun signal of land seismic stations and Ocean Bottom Seismometers.These experiments have filled the gaps in deep structure of land-ocean transitional area.The results show that the Binhai Fault Zone is a low velocity zone in the velocity structure,and reveal that the deep seismogenic structure of continental marginal seismic belt along the northern South China Sea is much involved in coupled function of low velocity zone in crustal structure and intersecting faults.The joint onshore-offshore deep seismic prospect links the crusts of land and sea perfectly;it can also construct the ultra long crustal structure profile across from the northern continental margin of the South China Sea and Xisha Block to Nansha Block.These experiments play an important role in revealing the structure of micro-blocks in Nansha Block,deep velocity structure of Nansha Block and its adjacent area,the integrated geophysical structure of Nansha Block and peripheral basin,and the transitional area between landmasses. Meanwhile,these experiments are conducive to know the current structural state and tectonic evolution history of Nansha Block and to interpret split-breakup process of Nansha Block.