东海西湖凹陷平湖斜坡带断裂系统特征及成因机制探讨

Fault system and its genetic mechanism in the Pinghu slope of the Xihu Sag in the East China Sea Shelf Basin

综合运用地震剖面解释结果和构造编图成果,对东海西湖凹陷平湖斜坡带断裂系统按发育规模和形成期次进行分类,分析了断裂系统的平、剖面展布特征,采用古落差法和活动速率法研究了断裂运动学特征,结合区域应力场特征探讨了其成因机制。结果表明,平湖斜坡带断裂系统可划分为4个断裂带,由北至南依次为孔雀亭同向断裂带、武云亭反向断裂带、平湖同向断裂带和平南堑式断裂带。平湖斜坡带以发育多米诺、地堑、梳妆、正牵引等伸展构造样式为主,局部(如平湖同向断裂带)见微弱反转构造。断裂运动学特征研究表明,断裂活动高峰期具有分带性,平湖同向断裂带断层活动性最强,孔雀亭同向断裂带和武云亭反向断裂带次之,平南堑式断裂带最弱。平湖斜坡带断裂系统的发生、发展是应力集中与断层间相互影响共同作用的结果,是对东海陆架盆地构造演化过程的局部响应。

By comprehensively using the results of seismic profile interpretation and structural diagrams, this paper classified the fault system by its development scales and stages in the Pinghu slope of the Xihu Sag in the East China Sea Shelf Basin, analyzing its lateral and vertical distribution characteristics. By using the method of fault throw and fault activity ratio, its kinematics are discussed, including its genetic mechanism combined with the regional stress field. The results show that the fault system in the Pinghu slope can be divided into four fault zones,including the Kongqueting synthetic fault zone, the Wuyunting antithetic fault zone, the Pinghu synthetic fault zone and the Pingnan graben-type fault zone from north to south. The Pinghu slope mainly developed under extension, such as domino-style, graben, comb, positive drag structures and others. While,weak inversional structure was only displayed in local scale, for example in the Pinghu synthetic fault zone. The fault kinematics showed that the peak period of fault activity had clear zonality. The strength of fault activity in the Pinghu synthetic fault zone was the most, the those of Kongquetin synthetic fault zone and the Wuyunting antithetie fault zone took the second place,while that of the Pingnan graben-type fault zone was the least. The occurrence and development of the fault system in the Pinghu slope was the result of stress concentration and the interaction between different faults, and was a local response to the tectonic evolution of the East China Sea Shelf Basin.