金沙江断裂带活动与大型滑坡群的关系研究:以金沙江拿荣—绒学段为例  

THE RELATIONSHIP BETWEEN ACTIVITY OF JINSHA RIVER FAULT ZONE AND LARGE-SCALE LANDSLIDES:A CASE STUDY OF THE SECTION BETWEEN NARONG AND RONGXUE ALONG THE JINSHA RIVER

作　　者：常昊 常祖峰[2] 刘昌伟 CHANG Hao;CHANG Zu-feng;LIU Chang-wei(Chongqing Institute of Geology and Mineral Resources,Chongqing 401120,China;Yunnan Earthquake Agency,Kunming 650224,China)

机构地区：[1]重庆地质矿产研究院,重庆401120 [2]云南省地震局,昆明650224

出　　处：《地震地质》2021年第6期1435-1458,共24页Seismology and Geology

基　　金：国家自然科学基金(U2002211,41472204);云南省青年地震科学基金(2019k08)共同资助。

摘　　要：文中从活动构造和灾害地质的角度调查并研究了金沙江断裂带的晚第四纪活动性,并着重分析大型滑坡与金沙江断裂带活动的关系。金沙江断裂带是一条规模宏大且长期活动的缝合线构造,是一条具有挤压性质的超岩石圈断裂带,上新世以来表现为右旋走滑运动,在曾大同、徐龙、尼中、里甫-日雨、郎中和古学沿线断层地貌清晰。地质调查和年代学测试结果表明,这些断裂断错了晚更新世—全新世堆积,在晚第四纪具有明显的活动迹象。研究区滑坡具有发生频率高、规模大、破坏性严重的特点。拿荣—绒学38km的沿江区段内在金沙江两岸共发育20余个特大型及大型滑坡,体积一般>1×10^(7)m^(3),有的>1×10^(8)m^(3),且几乎所有滑坡均位于活动断裂上及两侧1km范围内。这些大型滑坡群的发生与金沙江断裂带的长期活动、演化历史和复杂结构等有密切关系,它不仅使岩体结构变得支离破碎,且持续的活断层作用成为滑坡发生的主要原因。紧密相邻的断裂间、断裂交会的锐角区、断裂右向转弯部位和主断裂与横向断裂交会区等特殊构造部位,为构造应力易于集中、有利于特大型滑坡发生的关键部位。活动断裂对滑坡的控制作用不仅表现在大地震过程中,在非地震作用的自然状态下同样能导致大型滑坡密集发生。The relationship between large-scale landslides and active faults has attracted much attention.From the point of view of active tectonics and disaster geology,the late Quaternary activity of the Jinsha River fault zone is investigated and studied,and the relationship between large-scale landslides and activity of the Jinsha River fault zone is emphatically analyzed.The Jinsha River fault zone was formed during the closure of the Paleotethys Ocean.According to the distribution of the 5 km-wide ophiolitic melange zone,the ultramafic rock zone,and the local migmatization and progressive meta mor phism around the Variscan intermediate acid intrusive rock mass distributed along the fault,it is inferred that the fault zone was once a strongly active superlithospheric fault zone with obvious compressive properties.The Jinsha River fault zone is a large-scale,long-term active suture structure,with many branches,forming a 50 km wide structural fracture zone.Affected by the eastward compression of the Tibet Plateau,it has changed into a strike-slip fault zone characterized by dextral shear since Pliocene.In the study area,the fault landforms are clear along the Zengdatong,Xulong,Nizhong,Lifu-riyu,Langzhong and Guxue faults,which are mainly manifested as straight fault trough,linear ridge,fault scarp,and directional aligned fault facets.Results of field geological and geomorphological investigation and chronology show that the late Pleistocene and Holocene deposits are faulted,indicating the faults are active during the late Quaternary and dominated by dextral strike-slip with an average horizontal slip rate of 3.5~4.3 mm/a in Holocene.The study area is located in the middle and north of the world-famous Jinsha River suture of the north-south structural belt in Sichuan,Yunnan and Tibet,and the geological structural conditions are very complex.The main struc tural line is distributed in NS direction,interwoven with NE and NW faults and fold axes in network shape,and the structure is complex.Strong neotectonic movement,huge t

关 键 词：金沙江断裂带 晚第四纪活动 大型滑坡 特殊构造部位 关系 

分 类 号：P315.2[天文地球—地震学]