银川盆地西大滩隐伏断层晚第四纪活动特征

Activity Characteristics of Xidatan Buried Fault in Yinchuan Basin in Late Quaternary

摘要:

西大滩隐伏断层位于银川盆地北部,是石嘴山市活断层探测项目的目标断层之一。在浅层地震勘探的基础上,通过钻孔联合剖面探测和钻孔样品年龄测试,获得断层上断点埋深、主要标志层断距及沉积年龄等数据,估算了晚第四纪不同时段断层的滑动速率,结合地层变形情况探讨了该断层晚第四纪的活动特征。结果表明,西大滩隐伏断层自12 275±45aB.P.以来没有发生明显活动,属晚更新世末活动断层;晚更新世以来断层活动偏弱,平均滑动速率为0.024mm/a;除断层活动外,伴随着地层倾斜变形;两者均具间歇活动的特点,最小间隔约6 600a,最大间隔期12 275a。

Abstract:

The Xidatan buried fault is located in the north of Yinchuan basin and it is determined as one of buried faults in the active faults detection work of Shizuishan city. Based on the interpretation of seismic exploration for shallow layers, exploration of composite drilling section and core sample dating method are used to obtain some important data, such as depth of fault upper break- ing point, displacements and ages of key mark layer. The slip rates of Xidatan fault in different period of late Quaternary are finally estimated. The change of dip angle of key mark layer are found, and then, activity characteristics of Xidatan buried fault are discussed. The result shows that, with the deformation of the key mark layer, Xidatan fault ,which a low slip rate as 0. 024 mm/a, was a active fault in late Pleistocene and it＇s activity stop after 12 275±45 a B. P.. Not only offsets of the fault but also deformation of the key mark layer is characterized by intermittent activity. If considered these two changes as a whole, the minimum interval is 6 600 a and the maximum is 12 275 a.