【摘要】 在新一轮南黄海区域地质地震调查工作中,针对地震地质条件和勘探目标,设计了新的地震资料采集技术方案——上下源延迟激发+长排列接收,获得了强反射界面之下的深部地层有效反射,揭示了千里岩断裂两侧分布着向南逆冲的构造推覆带.结合重力、磁力反演成果认为,千里岩隆起区为扬子块体与华北块体碰撞接触带,扬子块体向北运动与华北块体碰撞后楔入到华北块体之中.更多还原

【Abstract】 Many geologists have studied the contact of the Yangtze block and North China block in the sea area with regional geological and geophysical methods.There are still different understandings.Combining regional geological data,we analyzed the contact relationships between these two major tectonic blocks in the sea area by acquisition,processing and analysis of multi-channel seismic data in the South Yellow Sea. According to the seismic geological conditions and exploration target,we designed a new air-guns array pattern of upper/lower sources which can effectively attenuate the effect of ghost in the low frequency range,broaden the bandwidth of seismic signal and promote the energy of low frequency components,based on theadvantage of the large penetration depth and long pathways for low frequency signal.For the exploration target layer of weak seismic reflection characteristics,we used long cable method receiving strong wide-angle reflection signal.The long spread of wide-angle reflection receiving method was used considering poor reflection in the target layer interiors,which permitted to achieve the strong energy wide-angle reflection at the large offset.The time-distance curve of wide-angle reflection with large offset is clear non-hyperbolic,which is difficult to focus on the effective stack data.We adopted the normal moveout correction of wide-angle reflection which was based on the anisotropic and the pre-stack time migration processing to achieve the impactful NMO,stacking and imaging of wideangle reflection.We obtained the deeper effective reflection that was below the continental sedimentary layer with the application of new seismic exploration technology.According to the seismic reflection characteristics and the regional geological background,the seismic reflection events in the southern Yellow Sea basin can be divided into four seismic reflection sequences in the new seismic imaging section.There are the Cenozoic continental facies seismic reflection sequence(S1),Mesozoic continental facies seismic reflection sequence(S2),Mesozoic-Paleozoic sediments seismic reflection sequence(S3)and basement seismic reflection sequence(S4).The S4 represents the Pre-Sinian metamorphic strata reflection and S3 is similar to marine facies strata seismic sequence calibrated by well data in the southern depress.It was another evidence for the speculation that the northern depression developed with Mesozoic-Paleozoic marine carbonate strata,characterized by large buried depth,great thickness and widespread distribution.In the Qianliyan fault,S4 seismic reflection sequences are underlain by that of S3,where a tectonic zone extends in direction of NE-SW.We conclude that there is a nappe structure zone trending NW-SE as shown by the synthetic interpretation of seismic,gravity and magnetic data.This zone distribution area was about 5000km2 in the basin south of Qianliyan fault,about 100 km distant to the biggest nappe,and the buried depth was about 3500~7500m.This nappe structure zone developed in the north of northern depression and uplift area north to the Qianliyan fault.The present and previous results show that the Qianliyan uplift was the contact zone between the North China block and the Yangtze block.The Yangtze block moved northward,which was embedded in the North China block after the continent-continent collision of the two blocks.The contact model between the two blocks is like a"Crocodile mouth".The seismic exploration method was used to study the shell structure.It can improve quality of raw seismic data and image accurately with innovative applications of technology and methods.We analyzed the contact model between North China block and the Yangtze block by using new seismic data and other geophysical data.The aim of this paper is to analyze the collision evolution process of Yangtze block and North China block in the sea area,and the control function of evolution formation for foreland basin with the application of OBS sections,gravity inversion results and magnetic data.更多还原