Geological Tectonic Features And Activity Analysis Of Aba Fault In West Sichuan

The Aba Fault zone in western Sichuan is located in Aba county,Aba Tibetan and Qiang Autonomous Prefecture.The study area is located in the Bayan Kera block in the eastern Qinghai-tibet plateau.In the past 80 years,the geological predecessors believe that the Songpan-ganzi fold belt was formed by the orogenic movement caused by the convergence of the south China plate,north China plate and qiangtang plate in the Mesozoic Triassic;The collision between Cenozoic Indian plate and Eurasian plate resulted in the uplift of the Qinghai-tibet plateau.Influenced by the sinistral strike-slip faults of east Kunlun and Xianshuihe and the dini-strike-slip thrust faults of Longriba in the region,the Bayan Karla block became an active zone of neotectonic movement in the eastern margin of the Qinghai-tibet plateau.In addition,the differential uplift and uplift of the crust in the Aba subsidiary block resulted in the formation of the present Aba sinistral strike-slip fault basin.The Longmenshan fault in the east,the East Kunlun fault in the north and the Xianshuihe fault zone in the north are also the areas with frequent earthquakes.The main research object of this paper is the basin-controlled fault and mid-basin fault of the southern margin and northern margin of the Aba basin.By collecting previous geological and geophysical research results,combined with article through high-resolution remote sensing interpretation,investigation of active fault routes,mapping of quaternary geology and geomorphology,section measurement,three-dimensional geomorphology measurement by unmanned aerial vehicles and other works.It is concluded that Aba fault is a sinistral strike-slip fault zone influenced by the NW trending East Kunlun fault and Xianshuihe fault,which is a NW spreading fault zone composed of the Volongningqin sinistral strike-slip thrust fault in the north margin,the Guoerkuhe sinistral strike-slip normal fault in the middle of the basin and the Arkehe sinistral strike-slip normal fault in the south margin of the basin.The Volongningqin fault in the north margin and the Arkehe fault in the south margin are the basin-controlling faults in Aba basin,which not only determine the source and distribution of sediments in the basin,but also determine the tectonic morphology of Aba basin,which is an asymmetric faulted basin with high in the north while low in the south and tends to the SSW.The uplift of different fault blocks in Cenozoic led to the uplift of the basement of the Aba basin on one side of the north-eastern boundary thrust fault and the subsidence on the other side of the normal fault near the south-western boundary.Based on the comparison of previous studies,this paper concludes that the basin-controlled fault was formed in the Miocene and the left strike-slip fault was active in the early-Pleistocene.The main active period of basin controlling fault is roughly determined to be the late-Pleistocene to date.However,there is an obvious correspondence between the seismic activity in Aba area and the seismic activity in Xianshuihe fault zone and Yushu fault zone,and the Ms8.0 Wenchuan earthquake in the eastern part of the Longmenshan fault zone,which is considered to have been inactive since the Late-Pleistocene,also reminds us that it is imperative and urgent to strengthen the study and monitoring of active faults.