Tectonic Deformation In Northern Tibetan Plateau Measured By InSAR Time Series

The collision between the Indian plate and the Eurasian plate has formed the largest and highest plateau on the earth,the Tibetan Plateau.The uplift and compression deformation has created and changed the tectonic pattern of the whole Eurasian continent.The northern boundary of the plateau is the leading edge of northward expansion and the most sensitive area to the plateau deformation.How did the deformation of controlling faults at the edge of the plateau distribute and evolve? How is deformation absorbed and transformed by different structures? How does the deformation migrate to adjacent faults? These problems are of great significance to the study of tectonic deformation and tectonic transformation in the northern part of the Tibetan Plateau.Large strike-slip faults and thrust faults dominate the present active tectonic model in the northern part of the Tibetan Plateau.To understand the present slip model and the location of strain concentration in the northern part of the Tibetan Plateau,it is necessary to quantitatively determine the slip rates of each tectonic unit and its segments.The InSAR time-series technique is used to study the temporal and spatial distribution of the slip rates of the Pamir-Tianshan collision zone,the Altyn Tagh fault zone,the Haiyuan fault zone and its adjacent faults in the northern Tibetan Plateau.Combining with the geodetic research results of the predecessors in this area,the relatively complete kinematic characteristics of the active structures in the northern Tibetan Plateau are extracted.Based on the research results of tectonic geomorphology,the tectonic deformation model in this area since late Cenozoic is analyzed,and the dynamic mechanism of tectonic deformation and the relationship between tectonic deformation and tectonic uplift in the northern Tibetan Plateau are discussed.The ESA satellite data covering the Pamir-Tianshan collision zone in 2003-2010 and 2014-2018 are collected.Four ENVISAT descending orbits(D191,D420,D148,D377),two ENVISAT ascending orbits(A055,A284),three Sentinel-1 ascending orbits(P027A,P056 A,P129A)and three Sentinel-1 descending orbits(P107D,P034 D,P136D)are processed by SBAS-based InSAR time series algorithm.The LOS-directional velocity field covering the Pamir-Tianshan collision zone is obtained on a long time scale.Based on edge dislocation model,simulated annealing method is used to invert fault motion parameters,and Monte Carlo method is used to estimate error distribution.The inversion results show that the South Atushi fault has been sliding steadily in the past ten years.The slip rate,locking depth and fault dip obtained from Sentinel-1 and ENVISAT velocity profiles are stable.Using ERS,ENVISAT and Sentinel-1 satellite data covering the Altyn Tagh strike-slip fault zone,including 24 ERS satellite descendig tracks,18 ERS satellite ascending tracks,24 ENVISAT satellite descending tracks,18 ENVISAT satellite ascending tracks,8 Sentinel-1 satellite descending tracks and 8 Sentinel-1 satellite ascending tracks,the interseismic strain accumulation of the Altyn Tagh fault is studied based on the time series InSAR analysis method.The slip rate and the locking depth of the Altyn Tagh fault zone are inverted using Savage dislocation model.In InSAR velocity field acquired from Sentinel-1 data,creep signals are identified.The creep velocity and depth are inverted by Fattahi model considering both deep slip and shallow creep.The results show that the Altyn Tagh fault zone is not completely locked.There exists creep motion with depth of 1-2 km and velocity of 1-2 mm/yr near 85°E.Using historical earthquake catalogue and geodetic model parameters,the geodetic moment accumulation rate and seismic moment release rate are calculated,the results show that the energy released by the Altyn Tagh fault zone accounts for only 1% of the accumulated energy,and the seismic risk is very high.Using ENVISAT and Sentinel-1 satellite data from ascending and descending tracks,including five ENVISAT descending tracks(D018,D104,D333,D061,D290),two ENVISAT ascending tracks(A240,A469),two Sentinel-1 ascending tracks(P128A,P055A),two Sentinel-1 descending tracks(P135D,P062D),differential interferograms are generated from two-pass D-InSAR method.After correction of unwrapping error,atmospheric delay,orbital plane,the average velocity and topographic error are estimated at the same time from the corrected interferograms.The strain accumulation of Haiyuan fault is studied based on InSAR velocity field.The spatial and temporal distribution of creep in Tianzhu seismic space is revealed.The deep slip rate and shallow creep rate are inverted simultaneously by Fattahi model,and the seismic risk of different segments of Haiyuan fault is evaluated.