Present-day Crustal Deformation Of The Maqinmaqu Segment In The East Kunlun Fault Zone Revealed By Sentinel-1 Images

The East Kunlun fault(EKF)is a lager active left-lateral strike-slip fault in the northern Tibetan Plateau.The slip rate of the eastern segment of the EKF decreases from west to east,however,it is controversial whether the slip rate of the eastern segment decreases slowly to the east from the west 98°E or rapidly to the east along～150 km toward its eastern tip.After the 2001 Kokoxili Mw 7.8 earthquake event,the Maqin-Maqu segment(MMS)located in the eastern EKF is recognized as a seismic rupture gap,exhibiting high potential for the occurrence of strong earthquakes.In this study,ascending and descending Sentinel-1 images of the MMS in the EKF were firstly adpoted to determine the interseismic Line-of-sight(LOS)deformation velocity field during 2014-2021 using the Interferometric Synthetic Aperture Radar(In SAR)technique.Then,both the three-dimensional deformation and strain rates field of the MMS were calculated from the integration of GPS and In SAR,and the horizontal deformation of the region was projected in the direction parallel to the EKF zone while the long-term slip rate of the MMS was retrieved using the screw dislocation model.Finally,the strain accumulation,long-term slip rate,and deformation characteristics of the MMS were discussed.The results are shown as follows:(1)The crustal deformation of the studied region is generally characterized by the eastward motion,and there is an obvious gradient zone between the two sides of the MMS in the LOS and east-west velocities,which decrease from west to east along the MMS.(2)The Anyemaqen Mountain region and Xigongzhou intersection zone have remarkable strain rates accumulation,and the current elapsed time since the last event is very close to the recurrence interval of the characteristic earthquakes,which indicates relatively high seismic risk.(3)Long-term slip along the MMS of the EKF from the Anyemaqen Mountain region to the east are 4.8±0.3 mm·a-1,4.5±0.2 mm·a-1,4.0±0.2 mm·a-1,and 2.5±0.3mm·a-1,respectively,showing that the long-term slip rate of the EKF likely decreases slowly near the Anyemaqen Mountain,which is at least 300 km from the eastern termination of the EKF.(4)The sub-blocks around the MMS of the EKF exhibit clockwise rotation,which is consistent with the bookshelf model.Namely,the regional deformation caused by oblique extruction of the northeastern Tibetan is accommodated and regulated by the left-lateral strike-slip of both the EKF and the nearby secondary faults,as well as the crustal shortening at the easternmost end of the fault.