中文摘要：

大歧口凹陷位于渤海湾盆地中部，是在中生代构造基础上形成的新生代构造单元，是我国最具勘探价值的大型富油气凹陷。前人对大歧口凹陷盆地结构、断裂构造、演化特征方面有了较为深入的研究，但对凹陷内主要断裂的分段活动特征、构造迁移，以及新生代基底走滑一盖层伸展构造体系的深浅部耦合关系并未进行全面细致的研究，这在一定程度上限制了对凹陷内断裂活动特征、构造成因机制、断裂拓展演化规律详细的构造分析。本文在精细解释、深入分析地球物理资料的基础上，开展了详细的构造研究。研究表明，歧口凹陷充填格局主控断裂为东西走向，近南北向的沿岸变换带是主变换带；新生代的构造体系受北东向右行基底走滑断裂和东西向的盖层伸展构造的双重控制，并形成三级断阶带。基底-盖层断裂的耦合方式主要有两种：一是在盖层中形成强制性褶皱传递基底走滑，二是在盖层中形成一系列雁列式正断层。欧亚板块下的地幔物质在印度板块和太平洋板块两大构造系统的共同作用下，自南向北迁移并上涌，导致歧口凹陷主要断裂的规模、活动期以及断裂活动由南西向北东迁移、演化。

英文摘要：

The Great Qikou sag is located in north-central area of the Huanghua depression, Bohai Bay Basin which is oil-gas-bearing faulted basin. Although previous studies has revealed the structures, fault systems and dynamic mechanisms of the Great Qikou sag, the segmentation, development and migration, activity of faults, the relationship between the basement-involved slipping fault systems and Cenozoic extensional fault systems in the Cenozoic sedimentary cover remain still unclear. It is vital for undstanding of the structural patterns of Cenozoic sedimentary cover. Based on interpretation and analysis of a large number of seismic profiles, we find the coastal transfer zone is south-north-striking, which means that the master faults are west-east- striking. Cenozoic fault system of the Great Qikou sag is mainly controlled by basement-involved strike-slip and extensional fault system in the sedimentary cover and developed three steps fault systems in the deep-profile. The coupling between basement-involved strike-slip and extensional fault systems has two cases： One is accommodated by forced folds related to strike-slip faulting, another is tranferred by a series of left-step NE-striking en echelon normal faults. The main faults, fault activity have a trend of southward migrating. Tectonic evolution and mechanism of the Great Qikou sag is the result of the Pacific plate eastward retrogressive subduction and the Indian plate progressive subduction, resulting in intensive fault activity of the migration from the southwest to northeast in the Great Qikou sag.