地震工程学报Issue(4)：986-995,10.DOI:10.3969/j.issn.1000-0844.2015.04.098
滇西南地区孟连断裂晚第四纪新活动特征初步研究
Preliminary Study on the Late Quaternary Activity Characteristics of the Menglian Fault in Southwest Yunnan
摘要
Abstract
Because it is located in an area of extensive collision between the Indian Plate and the Eurasian Plate,the Sichuan- Yunnan rhombic block in southwest Yunnan at the southeastern margin of the Tibetan Plateau is one of the regions with the highest concentration and frequency of strong earthquakes in China.Due to compression of this block in the SE direction,the region developed two groups of active transverse faults in NE and NNW directions.Both groups are in-volved in the process of rupture and the occurrence of earthquakes of above M7. 0.In this area, the main feature of the late Quaternary activity of these faults is strike-slip.The NW-trending faults have right-lateral strike-slip characteristics,whereas the NE-trending faults have left-later-al strike-slip characteristics.The Menglian fault is located in the boundary zone between south-west Yunnan and Myanmar.It is a large active fault in the south of the Sichuan-Yunnan rhom-bic block and its late Quaternary activity is intense.This fault has the main characteristics of left-lateral strike-slip with dip-slip.However,there are few research data on this fault and the extent of study has been low. <br> There are no records of earthquakes on the Menglian fault.However,in the southwest of the fault,a MS 7.3 earthquake occurred in the territory of Myanmar on July 12,1995,which may be related to its activity.The linear structure of the fault in satellite images and landforms is very clear.The stream and water system are obviously offset to the left side along the fault.According to scanning electron microscopy results of the characteristics of the surface of quartz fragments in gravel from a fault gouge and research into active faults,Weixian et al.(2002)believed that the Menglian fault was formed before the Pliocene,displayed a high frequency of activity in the late Pleistocene,and has been active since then. <br> Through an investigation of the active characteristics of the Menglian fault in the late Qua-ternary,this study aims to determine the structural transformation and obtain a mechanical inter-pretation of the active faults in different directions and natures in the study area.According to the interpretation of satellite images and field investigation,we found that the fault is 90 km long and has a trend of N70°E.The main landform due to fault dislocation is a linear fault scarp of unequal height,whereas the others are fault valleys,fault trenches,and fault passes.The horizontal dis-placement of gullies and terraces is of the order of tens of meters to several hundred meters.A large trench excavated in the west of Menglian County revealed many faults.Through analysis of the fault profile and 14 C dating results,we found that four paleoearthquake events have occurred on the Menglian fault.Except for the earliest events,the three that followed all occurred in the middle and late Holocene.The latest paleoearthquake occurred between (1860±30)and (1090 ± 30)a B.P.关键词
滇西南/孟连断裂/左旋走滑/古地震Key words
southwest Yunan/Menglian fault/left-lateral strike-slip/paleoearthquake分类
天文与地球科学引用本文复制引用
何文贵,刘兴旺,袁道阳,张波,吴明..滇西南地区孟连断裂晚第四纪新活动特征初步研究[J].地震工程学报,2015,(4):986-995,10.基金项目
地震行业科研专项(201108001) （201108001）
地震行业科研项目(201408023) （201408023）
