滇西南地区孟连断裂晚第四纪走滑速率的厘定  

Accurate Determination of the Late Quaternary Slip Rate of the Menglian Fault in Southwestern Yunnan

作　　者：刘炳旭 袁道阳[1,2] 王爱国 何文贵[1] 邵延秀[1,2] 方良好[3] 高效东 LIU Bingxu;YUAN Daoyang;WANG Aiguo;HE Wengui;SHAO Yanxiu;FANG Lianghao;GAO Xiaodong(Lanzhou Institute of Seismology,China Earthquake Agency,Lanzhou 730000,Gansu,China;Lanzhou National Geophysical Observatory,Lanzhou 730000,Gansu,China;Earthquake Agency of Anhui Province,Hefei 230000,Anhui,China)

机构地区：[1]中国地震局兰州地震研究所,甘肃兰州730000 [2]兰州地球物理国家野外科学观测研究站,甘肃兰州730000 [3]安徽省地震局,安徽合肥230000

出　　处：《地震工程学报》2019年第3期770-780,共11页China Earthquake Engineering Journal

基　　金：国家自然科学基金面上项目“滇西南地区龙陵—澜沧新生断裂带南段的走滑特征与构造转换”(41572197)

摘　　要：通过卫星影像解译和野外实地调查,获得滇西南地区孟连断裂的几何特征和活动性参数。孟连断裂总体走向NE-NEE向,不具有明显的分段性,连续性较好。断裂从单侧控制着沿线的勐滨、孟连和勐马三个新生代盆地的发育。断裂沿线地貌以线性较好的断层谷、断层崖和断层陡坎为主,并发育多级左旋位错的河流、冲沟和阶(台)地等,观测到的最小左旋位错约为7m。采用高精度Li-DAR测量方法,对4处典型水平位错地貌进行精细测量,根据获得的相应地貌面年代,得到孟连断裂晚第四纪以来平均左旋走滑速率为2.2±0.4mm/a。其结果与滇西南地区其他NE向左旋走滑断裂滑动速率相当,反映了区域构造活动的整体协调性。根据跨断层地质体最大左旋位错量9.5±1.8km,估算断裂开始左旋走滑的时代为距今4.7±1.6Ma左右,即中新世中晚期。Because of the limited extrusion of the Tibet Plateau from the northwest to southeast, the Sichuan-Yunnan block has one of the highest concentrations and frequencies of earthquakes in China. It is very critical to assess the seismic hazard and explore the geodynamics of this region by quantifying the slip rates of active faults as well as the earthquake occurrence. The Menglian fault, one of the active left-lateral strike-slip faults in Sichuan-Yunnan block, stretches from China to Myanmar. There are no records of earthquakes on the Menglian fault;however, many earthquakes occurred in its vicinity, which may be related to the activity of the fault, such as the Myanna M S7.3 earthquake of 1995. In China, the Menglian fault has a length of 90 km and a trend of NE-ENE. The fault shows clear geomorphologic characteristic with linear fault scarps (mainly), fault valleys, and fault trenches. Additionally, various offset streams, gullies, and terraces have been formed along the fault, and the observed minimum left-lateral dislocation is about 7 m. Using high-precision Li-DAR measurement, four typical horizontal dislocation geomorphologies were finely measured. According to the obtained age of the geomorphic surface, the average left-lateral strike-slip rate of the fault since the late Quaternary was (2.2±0.4) mm/a. The results were equivalent to the sliding rate of other NE-trending left-lateral strike-slip faults in southwestern Yunnan, reflecting the overall coordination of regional tectonic activities. According to the maximum left-lateral dislocation of (9.5±1.8) km, the initial time of the left-lateral strike-slip of the fault was estimated to be about (4.7±1.6) Ma, in the middle and late Miocene.

关 键 词：孟连断裂 左旋走滑 走滑速率 走滑起始时间 

分 类 号：P546[天文地球—构造地质学]