断裂带方解石脉ESR定年研究及其对龙蟠-乔后断裂剑川段活动性的指示  

ESR DATING OF CALCITE VEINS AND IMPLICATIONS FOR THE ACTIVITY OF THE JIANCHUAN SECTION OF THE LONGPAN-QIAOHOU FAULT ZONE

作　　者：姬昊 刘春茹[1] 魏传义[1] 杨会丽[1] 尹功明[1] 常祖峰[2] JI Hao;LIU Chun-ru;WEI Chuan-yi;YANG Hui-li;YIN Gong-ming;CHANG Zu-feng(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Yunnan Earthquake Agency,Kunming 650224,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [2]云南省地震局,昆明650216

出　　处：《地震地质》2024年第1期81-100,共20页Seismology and Geology

基　　金：国家重点研发计划项目(2021YFC3000601);国家自然科学基金(42172211,U1939201)共同资助。

摘　　要：龙蟠-乔后断裂带作为川滇菱形块体的一条大型边界断裂,构造运动强烈,地震活动频繁,发生多次5级以上地震,造成了重大的财产损失和人员伤亡,因此十分有必要加强对该断裂带的活动性研究,并评估其地震危险性。龙蟠-乔后断裂剑川段河南村断层剖面发育厚层方解石脉,为断层定年提供了十分宝贵的材料。文中利用ESR法对该剖面的方解石脉开展了测年研究,得到4件方解石脉样品(HNC-ESR01、HNC-ESR02、HNC-ESR03、HNC-ESR04)的年龄分别为(7.1±0.8)ka、(7.1±0.9)ka、(7.3±1.7)ka、(6.9±1.5)ka,年龄数据集中,平均年龄为(7.1±1.3)ka,指示该断层在不晚于距今(7.1±1.3)ka的时间段内发生过活动。年龄结果与该地区探槽工作揭示的古地震事件发生时间((6130±30)~(6320±40)a BP)在误差范围内吻合,表明断裂带方解石脉ESR定年是活动断裂和古地震研究的一种有效的年代学方法。但需要注意的是,ESR年龄仍存在误差较大的问题,在后续工作中需要进一步完善。另外,文中采用了5种拟合函数(LIN、SSE、DSE、EXP+LIN、D_(gamma))计算方解石脉样品的等效剂量值,结果表明,SSE函数提供了最佳的拟合效果。The Sichuan-Yunnan region is located in the southeastern part of the Qinghai-Tibet Plateau.Because of the compression and collision dynamics of the Indian Plate and the Eurasian Plate,the tectonic deformation is strong and seismic activities occur frequently.There have been many earthquakes above magnitude 7.0 in history.A series of active fault zones have developed in the region,among which the Sichuan-Yunnan rhombus block bounded by multiple active faults has attracted great research interests in recent years.The Longpan-Qiaohou fault zone is a boundary fault of the Sichuan-Yunnan rhombus block.The fault zone starts from Longpan in the north,passes through Jiuhe,Jianchuan,and Shaxi in the south,and ends at Qiaohou.It is about 120km long and the fault trend is 15°~20°.This fault zone is large in scale and highly active,with frequent seismic activity,complex mechanical properties,and variable movement patterns.The Mesozoic movement was intense.In the early Cenozoic,compression-thrust movement was dominant,and in the late Cenozoic,tension-strike movement was dominant.Since the Holocene,the fault zone has been characterized by left-lateral strike-slip movement with normal faulting properties,and earthquakes of magnitude 5 or above have occurred many times.Therefore,studying the activity of this fault zone is of great significance for the prediction and evaluation of regional strong earthquake risk.Thick calcite veins are well developed on the Henancun Fault of the Jianchuan section of the Longpan-Qiaohou fault zone,providing very valuable materials for fault dating.Calcite veins are coseismic rapid precipitation formed during seismic activity or syntectonic precipitation that filled along fractures after seismic activity.Therefore,their ages represent the latest time at which seismic activity occurred.Previous studies have shown that tensional fissures formed during coseismic events can close in a short period of time(days to months),suggesting that the filling of calcite veins within fault fissures is a relative

关 键 词：川滇菱形块体 龙蟠-乔后断裂 方解石脉 ESR定年 古地震 

分 类 号：P315.2[天文地球—地震学]