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采用钻探方法,同时结合新生代年代学方法对南口—孙河断裂进行了综合的探测研究。根据钻孔岩性、沉积相、沉积旋回、14C测年、磁化率等分析,确定了断裂北西段的位置及晚第四纪以来的活动特征。研究表明,主断层面位于钻孔L、G、K、B、J之间,倾向南西,下部倾角约60°,上部断裂分为两支,南支倾角约70°,北支约40°,上断点埋深约5.5m;在断层下降盘靠近断层处识别出了9个崩积楔,这代表了9次地震地表破裂事件,认为晚第四纪以来至少发生了9次古地震事件,距今年龄分别约为60470a、57150a、53271a、48100a、38760a、37820a、36250a、21920a、17500a;断层具有多期活动的特点,晚更新世晚期以来断裂平均滑动速率约0.26mm/a;该项研究得到的结果不仅对北京地区未来的地震安全性评估有重要意义,而且针对钻孔布设、地层对比、断层位错量估计、断层多期活动识别等关键性技术问题,采取了切实可行的改进方法,对于平原区隐伏断裂钻孔活动性研究有重要意义。
Using the drilling method, combined with the Cenozoic chronology method, the comprehensive exploration of the Nankou-Sunhe fault was studied. Based on the analysis of borehole lithology, sedimentary facies, sedimentary cycle, 14C dating and magnetic susceptibility, the location of the northwestern fault and the characteristics of activities since the late Quaternary have been determined. The study shows that the main fault plane is located between the boreholes L, G, K, B and J, with a southwestward inclination of about 60 °. The upper fault is divided into two branches with an inclination of about 70 ° in the south branch and about 40 ° in the north branch. The buried point of the fault is about 5.5 m deep. Nine collapsible wedges are identified near the fault depression plate, which represents 9 earthquakes. It is believed that at least 9 paleoseismic events have occurred since the late Quaternary. The age is about 60470a, 57150a, 53271a, 48100a, 38760a, 37820a, 36250a, 21920a and 17500a, respectively. The fault has the characteristics of multi-phase activity and the average slip rate of fracture since the late stage of Late Pleistocene is about 0.26mm / a. The obtained results not only have important significance for the future seismic safety assessment in Beijing area, but also adopt practical and feasible improvement methods for key technical problems such as drilling layout, stratum contrast, fault dislocation estimation and fault multi-phase activity identification , Which is of great significance for the study of drilling activity in hidden faults in the plain area.