Although the late Quaternary slip rate of the Northern Margin Fault of the Huaizhuo Basin(NFHB)was studied approximately 30 years ago using thermoluminescence and geomorphic methods,the underlying uncertainty cannot be neglected,considering the limitations resulting from age and displacement measurements.Accordingly,we attempted to re-estimate the late Quaternary slip rate of the NFHB using high-precision remote sensing image interpretation,large-scale geological and geomorphic mapping,paleoseismic analysis,and Quaternary geochronology testing.The results,based on stratigraphic dislocation and age constraint in the trenches,show that the present deformation of the NFHB has been dominated by the extension,with a vertical slip rate~0.04-0.11 mm/a.We estimate a vertical slip rate of~0.06 mm/a,with an R^(2) value of~0.91,which is much lower than the~0.5 mm/a result estimated previously.There are three possible reasons for this discrepancy.The fi rst is the limitation resulting from dating and displacement measurements in earlier studies;the second is the slip decomposition caused by multiple branches of the NFHB,which leads to the low slip rate observed at a single fault;and third possible explanation is that the fault may be locked at present with a low slip rate,which means that the earthquake hazard of the NFHB cannot be ignored,and more in-depth research,such as geodetic and intensive observations of earthquake precursors,is urgently needed.This discovery poses a new challenge for the active study of the NFHB and the northeast corner of the Ordos Plateau in the North China Block.
Li Lu-weiYu Zhong-yuanQiu Chun-miaoWang Wen-xuanZhao QianZheng Rong-yingYang Yan-Lin
格仁错断裂晚第四纪古地震研究是理解青藏高原中部构造变形与地震危险性评价关键环节。通过在格仁错断裂中段曲巴开展野外调查、无人机摄影测量、探槽开挖、光释光与碳十四测年工作,探槽揭露出5次古地震事件:E1(59.0±2.1 ka BP)、E2(57.1±2.2 ka BP)、E3(30.2±1.4 ka BP)、E4(12.5±0.6 ka BP)、E5(2.2~3.2 ka BP)。最新事件的离逝时间已超过2.2±0.3 ka,接近估算的M_(W)7.4地震复发间隔,指示格仁错断裂中段存在较强地震风险。
