旋转平面型正断层向铲式正断层的递进演化过程:以渤海湾盆地牛庄洼陷的断裂系统为例

Progressive transition processes of rotational planar normal faults to linked listric normal faults:A case study of the normal fault system in Niuzhuang sub-sag of Bohai Bay Basin

基于渤海湾盆地牛庄洼陷的3D地震精细构造解释成果,本文揭示了伸展盆地内部正断层由旋转正断层向连通的铲式正断层递进演化过程,该演化过程划分为4个阶段:以旋转平面型正断层为主要类型的初始阶段,以多米诺断阶为主要类型的发展阶段,以单条独立铲式正断层为主要类型的成熟阶段以及以连通铲式正断层为主要类型的高成熟阶段;并建立了在伸展量的递进增加且浅层存在滑脱层的地质条件下,旋转平面型正断层向铲式正断层递进演化模式。通过分析研究区剖面伸展量数据以及系列断层断距的变化,认为伸展量在不同级别断裂(主干断裂与次级断裂)之间的分配方式是研究区该递进演化过程的主控因素。本文提出的伸展盆地内部正断层递进演化过程及其模式将有助于丰富与完善伸展盆地正断层递进演化理论,同时也可为伸展量较大的背景下,正断层样式演化程度较低的现象提供一种新的成因解释。

Based on the precise interpretation of 3D seismic data in the Niuzhuang sub-sag of the Bohai Bay Basin,this paper reveals the transition processes from rotational planar normal faults to linked listric normal faults,which could be divided into four stages:1)the initial stage with the rotational planar normal faults as the main type,2)the development stage with a set of the rotational planar normal faults arranged in a domino style,3)the maturity stage with a set of the individual listric normal fault arranged in a domino style,and 4)the high-maturity stage with a set of the linked listric normal faults to be dominant.The progressive evolution mode of these normal faults is also established.By analyzing the local extension data of the study area and the net-slip amount of these faults,it is suggested that the partition of extensional amount between the primary fault and secondary faults,rather than the total amount of extension,plays a pivotal role in the transition processes.