中文摘要：

东海陆架盆地位于欧亚板块东缘,受太平洋板块俯冲、印度板块与欧亚板块碰撞影响,经历了3期构造反转作用,尤其是位于其东部拗陷带的西湖凹陷,记录了新生代以来的构造反转过程。选择反转作用最为强烈的西湖凹陷中北部区域,进行有限元数值模拟,以此为基础来探讨反转构造的动力学机制。在大量地震剖面的综合分析的基础上,基于西湖凹陷的构造几何学特征,建立了具有黏弹性性质的6套地层以及9条主要断裂组成的地质模型。模拟结果表明,在西湖凹陷中以剪切为主并辅以早期拉伸、晚期挤压的凹陷演化模式是控制凹陷构造反转过程自西向东逐渐发生迁移的主要因素。西湖凹陷垂向位移场演化特征的定量化分析表明,反转构造过程表现为第一期反转导致西部隆升、东部沉降,第二、三期反转导致西部沉降、中东部隆升的特征,模拟结果与西湖凹陷不同界面剥蚀厚度显示的区域隆升及沉降演化过程一致,且模型中压性应力场低值区的分布与已知油气藏的分布也具有较好的对应关系。因此,西湖凹陷构造反转过程主要受区域应力场由早期的右行张扭逐渐调整为晚期的左行压扭影响。造成这种调整的原因主要是太平洋板块、菲律宾海板块向欧亚板块的俯冲速率及方向的改变。

英文摘要：

The East China Sea Continental Shelf Basin is a large basin located in the eastern border of the Eurasian Plate. Under the effects of the India-Eurasia collision and the subduction of the Pacific Plate, this region has experienced three-stages of tectonic inversions since Cenozoic, especially in the Xuhu Sag. This paper presents a numerical simulation results by finite element method to the north-central Xihu Sag in an attempt to investigate the mechanism of tectonic inversion. Based on the comprehensive structural analysis and the structural geometry of the sag established with a large number of seismic profiles, a viscoelastic geologic model of 6 layers and 9 major faults was constructed for the Xihu Sag. Simulation results show that the subsidence caused by the shearing movement characterized by transtension in early stage and transpression in later stage is the major force controling the inversion process and its propagation from west to east. Based on quantitative analysis of vertical displacement field of the Sag, this paper identified a tectonic inversion process with uplifting in the west and subsiding in the east after the first-stage of inversion; and then subsiding in the west and uplifting in the middle and east after the second and third-stages. The simulation results are well consistent with the process of uplifting or subsidence obtained from the de- nudation thickness and the distribution of low compression stress, displaying certain correlation with the distribution of oil reservoirs. The results indicate the plausibility of similar deformation controls. In conclusion, the formation of the tectonic inversion in the Xihu Sag is controlled by the adjustment of the stress field from dextral transtension to sinistral transpression caused by the change in subduction rates and direction of the Pacific Plate and the Philippine Sea Plate.