运城盆地盐湖南岸断层晚第四纪活动特征研究

STUDY ON THE ACTIVITY CHARACTERISTICS OF THE SOUTH BANK FAULT OF YUNCHENG SALT LAKE IN YUNCHENG BASIN SINCE THE LATE QUATERNARY

盐湖南岸断层位于运城市盐湖南岸,在浅层地震勘探的基础上,通过钻孔联合剖面勘探和钻孔样品年龄测试,获得断层的上断点埋深、断层标志层的断距以及地层沉积年龄等数据,在此基础上分析了盐湖南岸断层的晚第四纪活动特征。研究表明,盐湖南岸断层在55.7±0.43 ka B.P.以来没有发生明显的活动,断层的活动时代为晚更新世早、中期。断层在晚第四纪以来经历过2次构造活动期和2次间歇期,间歇时间为约16000 a和55700 a,在2次活动期间断层活动程度存在差异,晚更新世早期断层活动较强,中期活动相对减弱。晚更新世以来断层的平均滑动速率为0.0276 mm/a,属弱活动断层。

The south bank fault of Yuncheng Salt Lake is located on the south bank of Yuncheng Salt Lake in Yuncheng City(35.02°N,110.98°E).To further investigate its activity characteristics since the Late Quaternary,the borehole profile exploration together with the dating of borehole samples were carried out based on the shallow seismic exploration.The fault activity characteristics since the Late Quaternary was then analyzed in terms of the buried depth of the upper breakpoint of the fault,the distance of the fault marker layer and the sedimentary age of the stratum.The results indicate that since 55.7±0.43 ka B.P.,no obvious activity has happened in the South Bank Fault of Yuncheng Salt Lake,and the activity age of the fault is the early and middle stage of the Late Pleistocene.The fault has experienced two periods of tectonic activity and two periods of intermittence since the Late Quaternary,with the intermittent of ca.16000 a and 55700 a.However,during the two activities,the degree of fault activity was different.In the early stage of Late Pleistocene,the fault activity was obviously stronger than that in the middle stage.The average slip rate of the fault since the Late Pleistocene is 0.0276 mm/a,which is a weak active fault.