川西理塘-义敦断裂措普湖段第四纪晚期滑动速率与古地震序列  

Late quaternary slip rate and paleoseismic sequence of the Cuopuhu section of the Litang-Yidun fault,western Sichuan,China

作　　者：王世元[1] 王竞 李福鹏 陶志刚[2] 梁明剑[1] 刘韶[1] 屈淼 张力文 曾维祖 晋云霞 WANG Shiyuan;WANG Jing;LI Fupeng;TAO Zhigang;LIANG Mingjian;LIU Shao;QU Miao;ZHANG Liwen;ZENG Weizu;JIN Yunxia(Sichuan Earthquake Agency,Chengdu 610041,Sichuan,China;School of Mechanics and Civil Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China;Panzhihua Earthquake Monitoring Center,Panzhihua 617000,Sichuan,China)

机构地区：[1]四川省地震局,四川成都610041 [2]中国矿业大学(北京)力学与建筑工程学院,北京100083 [3]四川省地震局攀枝花地震监测中心站,四川攀枝花617000

出　　处：《地质力学学报》2024年第2期275-288,共14页Journal of Geomechanics

基　　金：国家自然科学基金项目(2019QZKK0708);中国地震局星火计划(XH24036B);中国地震局地震工程与工程振动重点实验室重点专项(2021EEEVL0101)。

摘　　要：理塘-义敦断裂是川滇菱形块体内部一条延伸约130 km的全新世活动的左旋走滑断裂带,是川西理塘地区地震活动的重要控震构造,目前其北段的措普湖段研究程度相对较低。将理塘-义敦断裂措普湖段作为研究对象,运用野外勘察、高精度测绘、探槽与14C测年等方法对措普湖段进行滑动速率和古地震探究。开挖的2处探槽位于冬欧山坡麓处,通过识别探槽内断裂与地层的切割关系、地层沉积特征、断层运动性质等标志;共识别出4次古地震事件:事件Ⅰ发生于BC 3382±60 a之前;事件Ⅱ发生于BC 3382±60 a~BC 1094±51 a之间;事件Ⅲ与事件Ⅳ均发生于AD 1330±44 a之后。可以推断理塘-义敦断裂措普湖段具有大概率的古地震复发间隔为2.4 ka左右,不排除有小概率复发间隔0.4±0.3 ka的可能。理塘-义敦断裂措普湖段古地震事件与大毛垭坝段和理塘段古地震事件之间存在差异,但是不同分段断裂的地震活动性在全新世以来均表现出持续增强趋势。根据测绘断错地貌和末次冰期冰碛垄推算出晚更新世以来措普湖段平均滑动速率为4.15±0.5 mm/a,与理塘-义敦断裂第四纪晚期不同分支滑动速率处于同一量级水平。文章完善了理塘-义敦断裂的构造特征全貌和古地震、滑动速率等信息,有助于更好地理解该断裂及该地区地震活动史和构造变形模式,为今后地震的中长期预测提供更多的数据,同时也有助于川藏铁路沿线相关工程的地震风险评估。[Objective]The Litang-Yidun fault is a left-lateral strike-slip active fault zone extending approximately 130 km in the Sichuan-Yunnan rhombic block in the Holocene.As a significant seismogenic structure controlling seismic activity in the Litang area of western Sichuan,research on both paleoseismicity and surface ruptures primarily focuses on the Litang and Damaoyaba sections,with relatively limited study on the Cuopuhu section in the northern part.Detailed investigation of the Cuopuhu section can provide fundamental information on its activity characteristics,paleoseismic events,and slip rates.[Methods]The Cuopuhu section of the Litang-Yidun fault was investigated using field surveys,high-precision mapping,trenching,and 14C dating methods to explore its slip rate and paleoseismic events.Two trench sites were excavated at the foothills of Dongou Mountain to identify the relationships between faulting and strata,sedimentary characteristics,and fault motion.[Conclusion]Four paleoseismic events were identified:EventⅠoccurred before BC 3382±60 a;EventⅡoccurred between BC 3382±60 a and BC 1094±51 a;EventsⅢandⅣoccurred after AD 1330±44 a.The recurrence intervals of the four earthquakes are approximately 0.4±0.3 ka,2.42±0.1 ka,and 2.40±0.1 ka,respectively.Based on the calculated intervals,EventsⅠandⅡ,and EventsⅡandⅢ,Ⅳ,have recurrence intervals of about 2.4 ka.EventsⅢandⅣoccurred after AD 1330±44 a,making it difficult to determine their sequence and exact timing.It can be inferred that the Cuopuhu section of the Litang-Yidun fault likely has a recurrence interval of about 2.4 ka for paleoseismic events,with a possibility of seismic events with recurrence intervals of 0.4±0.3 ka.By comparing the research data between the Cuopuhu section and the Litang and Damaoyaba segments,differences in paleoseismic events between the Cuopuhu section and the other sections are evident.However,the seismic activity of different fault sections has shown a sustained strengthening trend since the Holocene.Base

关 键 词：活动断层 理塘-义敦断裂 古地震 运动速率 措普湖 青藏高原东缘 

分 类 号：P546[天文地球—构造地质学] P65[天文地球—地质学]