渤西地区新生代断裂体系特征及形成演化

The Characteristics and Evolution of the Cenozoic Fault Systems in the Western Bohai Sea Area

为明确渤西地区新生代断裂体系发育特征,利用最新的三维地震资料及钻井资料,通过地震切片、方差体切片、断层活动速率等技术方法,重点从断裂几何学特征、性质及样式、运动学特征、构造演化动力学背景等方面对渤西新生代断裂体系发育特征进行了精细刻画。结果表明:研究区断裂发育存在北东、北西和近东西向三个优势方向,早期(古近纪)以发育张性断裂为主,后期叠加走滑作用,使得断裂复杂化;渤西地区新生代断裂体系演化经历了古新世-早始新世末的初始伸展、始新世中晚期强烈伸展、晚始新-早渐新世弱拉张-弱张扭、中-晚渐新世张扭-走滑、上新世至今强走滑等五个阶段。渤西地区新生代多期次、多阶段、不同性质复杂断裂体系是受区域应力场、沙垒田古隆起、基底先存断裂等因素综合作用的结果。

In order to clarify the development characteristics of Cenozoic fault system in the western Bohai Sea area,the seismic slice,variance slice and fault activity rate were used to illustrate the properties of fracture geometry,fault types and structure style,kinematic characteristics and dynamic background of tectonic evolution,based on the latest well logging and high-quality,three dimensional(3-D)seismic data.The results show that the fault systems are predominantly NE trending,EW trending and NE trending.Tensional fault is the main type in the Paleogene,and later strike-slip complicates the faults.A five-stage dynamic evolution model for the faults system was presened:the initial extension in the Paleocene to the end of the early Eocene,strong extension in the middle and late Eocene,weak tensioning and weak strike-slip in Late Eocene to early Oligocene,tensional twisting and strikeslip in middle-Late Oligocene,strong strike-slip stage in Pliocene to the present.It is concluded that the multistage development and complex properties of the fault system in the Western Bohai area are affected by the regional stress field transformation,the Shaleitian uplift and the pre-existing basement faults.