Study On Crustal Deformation Characteristics Of Xianshuihe Fault Zone Based On SBAS-InSAR

The Xianshuihe fault zone is located in the western part of Sichuan Province on the eastern Qinghai-Tibet Plateau.It is the boundary zone between the Sichuan-Yunnan rhomboid block and the Bayankala block.It is a northwest-trending arc-shaped strike-slip fault zone with active tectonic movement.The movement has obvious segmentation characteristics.The north-south section has a larger slip-slip rate and exhibits the characteristics of creeping movement.The south-east section has a significantly smaller slip-slip rate than the north-west section.The Xianshuihe fault zone and its nearby areas have frequent strong earthquake activities.It is of great significance to study the spatiotemporal characteristics of the current crustal deformation for seismic risk assessment,and at the same time provide effective support for the location of major engineering projects in the region and disaster prevention.Using InSAR technology to obtain the crustal deformation field with high spatial-temporal resolution can be used to study the fine deformation characteristics and movement modes of the fault zone and surrounding areas.In this paper,the data of 142 scenes of Sentinel-1A ascending from 2015 to 2019 and 27 scenes of ALOS-1A from 2006 to 2010 are used to obtain the LOS-oriented deformation velocity field of Xianshuihe fault zone in two periods based on SABS-InSAR technology;3 scenes of Sentinel-1A orbit-increasing data are based on the D-InSAR technology to obtain the deformation field of the 2014 Kangding Ms6.3 earthquake and invert the source parameters;the different sections of the Xianshuihe fault zone before and after the 2014 Kangding earthquake were studied Deformation characteristics,strike-slip rate and locking depth,the following conclusions are obtained:1.The LOS direction deformation rate of the Xianshuihe fault exhibited left-handed movement characteristics.The deformation between the two discs is obvious.The northeast disc is uplifted and the southwest disc is settled.The northeast disc velocity in the northwest segment from 2006 to 2009 was6.79mm/a¹4.35mm/a,the velocity of the southwestern disc was-7.36mm/a^-15.26mm/a,and the velocity of the northeastern disc of the southeast segment in2007²010 was 4.14mm/a⁸.18mm/a,and the velocity of the southwestern disc was-3.35mm/a^-7.68mm/a,from 2015 to 2019,the northeast plate velocity in the northwestern region was 9.79mm/a¹3.17mm/a,the southwest region velocity was-8.24mm/a^-14.35mm/a,and the northeast region velocity in the southeast segment was 2.55mm/a⁷.52mm/a,the velocity of the southwestern disc was-3.69mm/a^-8.17mm/a,and there were obvious velocity gradients on both sides of the northwestern section of the fault zone.2.In 2014,the Ms6.3 earthquake co-seismic deformation field of Kangding was-83.711mm⁹4.687mm.The source parameters based on the Okada model inversion were as follows:the sliding angle was 10.12°?the focal depth was 24.4km?the inclination was 88.27°?the strike was 146.72°?the magnitude was Nw6.2?and the earthquake rectangle was 2.09×10¹⁸Nm.3.The deformation rate in the upward direction of the LOS was calculated along the fault zone parallel to the inversion.Based on the two-dimensional dislocation model,the strike-slip rate and blocking depth of the five sections were reversed from northwest to southeast at different time.The results show that:1)2006²010 The annual slip rates were 14.41mm/a,12.76mm/a,5.62mm/a,5.75mm/a,5.94mm/a,and the blocking depths were 6.35km,7.32km,6.31km,14.57km,15.2km;2)The sliding rate ranges from 2015 to 2019 were 13.04¹5.15mm/a,13.04¹6.01mm/a,2.87⁹.15mm/a,4.0⁶.55mm/a,4.0±1.84⁷.15mm/a,blocking The depths were8.03km,6.97km,7.1km,15.23km,and 18.1km respectively.3)The slip rate gradually decreases from the northwest to southeast,and the blocking depth gradually deepens.The northwest segment has shallow creep.4.The crustal deformation characteristics from 2006 to 2010 indicate that the northwest section was shallow creeping before the Kangding Ms6.3 earthquake in2014,and the stick-slip movement was from the southeast section;the crustal deformation characteristics from 2015 to 2019 showed that the northwestern part within five years after the earthquake The section continued to maintain shallow creep,and the south-east section exhibited creep characteristics from 2015 to 2017,with a walk-slip rate of 9.15±2.45mm/a,which was in the post-earthquake recovery stage,and the creep phenomenon disappeared from 2018 to 2019,and new One round of inter-earthquake strain accumulation;the northwestern section of the Xianshuihe fault showed creeping motion characteristics,and the earthquake occurred was a creeping type earthquake;the southeast section showed viscous sliding motion characteristics,and the occurring earthquake was a sticky slip type earthquake.