Study Of The Deformation Characteristics Of The Central-western Segment Of The East Kunlun Fault Zone Using Combination InSAR And GPS Observation Data

The East Kunlun Fault Zone is a large left-handed sliding lithosphere fault zone formed in the interior of the Qinghai-Tibet Plateau along the stitches of the East Kunlun ancient tectonics during the dive of the Indian plate to the Eurasian plate.It is also a boundary active fault between the Chaidamu block and the Bayan Kala block in the northern Qinghai-Xizang Plateau,with a total length of about 2000 km.Along the East Kunlun fault,strong earthquakes with M ? 7 occurred along the East Kunlun fault,such as Xiugou M7 in 1902,Toso Lake M7.5 in 1937,Dari M7.7 in 1947,Arak Lake M7 earthquake in 1963 and Shenza Rusjiudo M7.3 on the adjacent Margai ChakaRuolaca fault in 1973.The study area of this paper is the Kunlun Mountain pass-Arak Lake section,ranging from 93 °E to 97.5 °E.The strike-slip rate in this area is large,and it is also an area where the slip rate decreases obviously from west to east.Previous studies have shown that there is a possibility of seismogenesis in this area.therefore,it is of great significance to study the activity characteristics of the East Kunlun fault zone in this area.In this paper,based on the Sentinel-1A/ B desending data from 2015 to 2020,a large range of surface LOS deformation results are obtained by using PS-InSAR technology,and the InSAR deformation field is downsampled.Then,based on the negative dislocation model,using the InSAR deformation field and the 1991-2015 GPS velocity field,the fault locking degree and slip loss distribution in the central and western section of the East Kunlun fault zone are respectively calculated by TDEFNODE software.Combined with the temporal and spatial distribution of earthquakes,the movement state of the East Kunlun fault zone in the study area is analyzed and studied in order to understand the deformation mechanism of the East Kunlun fault zone.The current crustal movement and deformation characteristics of the Qinghai-Xizang Plateau and even the whole Qinghai-Tibet Plateau provide support.The main conclusions of this paper are as follows:1.The InSAR LOS deformation rate and GPS velocity field show that the East Kunlun fault in the Kusai-Arake Lake section in the study area is mainly sinistral strikeslip movement,and the fault strike-slip rate is about 9-12mm/a.The analysis of GPS velocity field shows that the velocity difference of block movement on both sides of the fault is mainly parallel to the direction of East Kunlun fault,that is,the velocity difference in east-west direction and north-south direction is small.The InSAR LOS directional deformation field shows that the slip rate of Jiangcuo fault is higher than that of East Kunlun fault.2.Based on the negative dislocation model,the inversion of fault locking degree and slip deficit rate of East Kunlun fault zone using InSAR data and GPS data shows that the complete locking depth of Kusai Lake-Xidatan section of East Kunlun fault zone is about 10 km and that of Arak Lake section is at 25 km.The slip deficit rate and seismic moment accumulation rate also show the same distribution characteristics,and the slip deficit rate is about 12-16mm/a.The fault locking calculated by InSAR data from 2015 to 2020 is stronger than that calculated by GPS data from 1991 to 2015,and the fault locking range extends from east to west.From the distribution of fault locking and slip deficit rate calculated in different time periods,the fault locking of Kusai LakeEast-West Datan is low,and the possibility of earthquake in the future is small.The distribution of fault locking,slip deficit rate and seismic moment accumulation rate in the Arak Lake section also shows that the seismic risk of the Arak Lake section is higher than that of the Kusai Lake-Xidatan section.In addition,the Mado Ms7.3 earthquake in 2021 is close to the Arak Lake section of the East Kunlun fault zone,which may be affected by this earthquake and has the possibility of earthquake occurrence.3.Through the earthquake distribution map,it is found that the earthquakes in the study area are distributed from west to east along the east Kunlun fault and Jiangcuo fault with time.The earthquakes in the western region are mainly the Kunlun Mountain pass earthquake and its aftershocks in 2001.Before the Maduo Ms7.3 earthquake in2021,the earthquakes were distributed along the east Kunlun fault and Jiangcuo fault to 96 °east longitude from west to east,and almost no earthquake occurred in the eastern region.Compared with the degree of fault locking,earthquakes are mainly distributed in the incomplete locking area,so it can be inferred that the earthquake occurred in the Kusai Lake-Xidatan section released the accumulated strain energy of fault locking,resulting in a small degree of fault locking.In the future,the locking depth of the East Kunlun fault in the west of Arak Lake may continue to extend to the west,and there is also the possibility that earthquakes occur,strain energy is released,and the temporal and spatial distribution of earthquakes continues to expand eastward.