A Study On The Activity And Stream Analysis Of Litang Fault Zone Based On GIS Data

Litang fault zone is the secondary shear rupture zone in Sichuan-Yunnan block,it has the characteristic of the sinistral strike-slip movement.The fault zone shows astrong activity since the Late Quaternary and M7.3earthquake had occurred in1948.A series of small Quaternary basins distributed along the fault zone whichcontrol the formation and evolution of these basins, the shape of the basin and itsCharacteristics of internal stream to reflect the strength of the fault activity. This paperresearched the activity of Litang fault and provided more reliable basis of informationfor seismic performance,engineering stability and seismic safety evaluation.In order to investigate the Late Quaternary activity of Litang fault zone, based onSRTM DEM data, author did a statistical analysis using the GIS software to extractdrainage system of the study area and the basin, measured the1948M7.3earthquakesurface rupture with DGPS and interpreted the typical dislocation geomorphologybased on Google images.This paper discussed river system analysis andmicrogeomorphology quantitative analysis of fault zones. The main conclusions areas follows:(1)Statistics shown that: In the Litang fault zone control,the water system of thestudy area display the regular exhibition.The spread direction of Quaternary basinRiver distribution along the fault zone is either nearly parallel or nearly orthogonal tothe fault zone and the strength of the active faults resulting the river systemcharacteristics on both sides of basin, including srteam length,linear density Streamgradient,are very different.By active faulting which side of the river systems havesingle direction, shorter length, denser distribution, larger longitudinal gradient,thecontrary other side of the river systems have diverse direction,longer length, sparseand tortuous distribution,smaller longitudinal gradient.(2)This paper from the water system analysis and surface rupture zone statisticstwo aspects deduce the new regional tectonic stress field of the study area.The streamadvantage direction of the region as a whole combination of characteristics and the assembled fractures show that the principal stress direction of regional tectonic stressfield is nearly east-west.(3)The interpretation of faulting landform in northern Dewu and eastern Cuopulake suggest that the fault activity is strong since the Last Glacial?the fault occurredmulti-phase destructive seismic events and accumulated different leveldisplacement.The statistics shown that, the total length of fractures is about35km,themain type of the fractures is R with strike316°;while the main fault strikes332°,thesurface ruptures trending NNW which run from the northern Dewu,along thesouth-west edge of the Dewu basin and north-east edge of Zangba basin,to the Xiaruvillage at the south side of Wulianghe river,and the lengthy density of the fracturesindicate that the maco-epicenter lies in the middle of the Dewu basin.