Crustal Deformation Characteristics In The Red River Fault Zone And Surrounding Areas Based On GPS Observations

The Red River fault is a large fault on the southeastern margin of the Tibetan Plateau and control the tectonic movement in Yunnan.Seismic activities are frequent in the northern part of the Red River fault zone,and seismic activity is exiguity in the middle and southern parts.The earthquakes are frequent near the Chuxiong-Jianshui,Xiaojiang,Wuliangshan and Lancangjiang fault.Using of GPS technology to study the crustal deformation characteristics of the Red River fault zone and surrounding areas is of great significance for regional earthquake prevention and disaster reduction.This article is based on multiple periods GPS observation data from 1999 to2015.Taking the Red River fault zone and the surrounding area as the research object.Studying the horizontal and vertical movement characteristics of the area and obtaining the horizontal internal movement characteristics by deducting the region's overall rigid movement rate.Using grid interpolation method to calculate the current strain accumulation and the Euler rotation motion of the region,and discuss the relationship between the current strain accumulation condition and the earthquake.Using the screw dislocation model and the negative bulk dislocation model in the elastic half space to obtain the slip rate and locking distribution of the main fault.The results of the two models are compared with those of other scholars.The main research contents and results of this article are as follows:(1)Using the collected multi-phases of GPS data,the horizontal movement and vertical deformation characteristics of the area are obtained.Considering that the velocities field under the Eurasian reference frame include the overall rigid motion of the region relative to the stable Eurasian plate.In order to show the differences in horizontal movements within a good display area.We use strict methods to eliminate the overall rigid motion of the area.The results show that the horizontal movement of the region has the characteristics of weak north and strong south,weak strong eastand weak.Comparing with the vertical movement of the internal reference station KUMM,the overall area is uplifted.Comparing with the basic site JB25 in the South China block,the whole area are in settlement.The horizontal movement of the northern section of the Red River fault zone,the two sides of the southern section of the Red River fault zone and the intersection with the Xiaojiang fault zone are obvious,and the internal movement on both sides of the middle section of the Red River fault zone is weak.(2)The GPS sites are decentralized.In order to obtain continuous strain rate and Euler rotation,two-dimensional "high-tension spline" is used to interpolate the GPS velocity field.The results show that the tensile strain in the region is near the east-west direction and the compressive strain is near the north-south direction.The northern and southern sections of the Red River fault zone(Yuanyang),the Chuxiong-Jianshui fault zone,the southern section of the Xiaojiang fault zone and the east side of the Wuliangshan fault zone are strongly strain areas.The middle part of the Red River fault zone,the north part and the middle part of the Xiaojiang fault and the northern part of the Wuliangshan are weakly strain area.With the west branch of Xiaojiang fault zone and the southern segment of Red River fault zone as the boundary.The east of Xiaojiang fault zone,the south segment of Red River fault zone are mainly anticlockwise rotation,the west of Xiaojiang fault zone,the north and middle of Red River fault zone are mainly clockwise rotation.(3)Regional horizontal and vertical movements,strain accumulation,and Euler's rotating motion characteristics show that the deformation features of the Red River fault zone have obvious segmental characteristics.The north part of the horizontal movement rate is 11.1mm/a,take the tensioning movement as the main part,the accumulation of high strain,the Euler movements show clockwise rotation.The middle of the horizontal movement rate is 9.3mm/a,tension more obvious movement,strain accumulation is weak,the Euler rotary movement is clockwise.The southern section of the horizontal movement rate is 8.1mm/a,mainly to extrusion movement,the accumulation of strong strain,Euler rotary motion is anticlockwise.(4)Based on the model of spiral dislocation in elastic half-space and themodel of negative displacement of block,the strike-slip rate and locking depth of the main fault zones are inverted,and the Red River fault zone strike-slip rate and locking depth are small.The Xiaojiang fault zone has the largest strike-slip rate and locking depth.The Right-handed strike-slip rates of the north,middle and south sections of the Red River fault zone are(4.7±0.8)mm/a,(3.2±0.6)mm/a and(2.9±0.2)mm/a,with a locking depth of 10.9 km.11.5km,12.6km.The strike-slip rates of the Chuxiong-Jianshui fault zone,the north,middle and south sections of the Xiaojiang fault zone,the Wuliangshan fault zone and the Lancangjiang fault zone are(4.4±0.4)mm/a,(10.1±0.2)mm a,(10.3±0.2)mm/a,(10.3±0.1)mm/a,(3.5±0.6)mm/a and(4.8±0.5)mm/a,with locking depth of 17.6km,20.7km,23.1km,21.9km,11.7km and 13.4km.