Study On Observations Of Coseismic-Interseismic Deformation And Kinematic Inversions Of Fault Parameters Using GPS And InSAR

In the past two decades,the rapid development of GPS and InSAR technology has become an important means of surface deformation monitoring.It has the advantages of high spatial resolution,wide coverage,high accuracy,all-day and all-weather,and can efficiently obtain high-precision surface deformation information,so it has been widely used in deformation monitoring of earthquake cycles.Based on GPS and InSAR technology,this paper takes the 2017 Mw6.5Mainling earthquake and the Elashan fault as research objects,and study the coseismic and interseismic deformation.The main research contents and conclusions of this article are as follows:?1?On 17 November 2017,a Mw 6.5 earthquake occurred in Mainling County,Nyingchi City,China.The epicenter was located in the Namche Barwa region of the eastern Himalayan syntaxis.Here,we have derived coseismic deformation from Global Positioning System?GPS?data and ascending Sentinel-1A Synthetic Aperture Radar?SAR?data.Based on a joint inversion of the two datasets,we obtained the coseismic slip distribution along a curved,northeast trending,and high-angle?dip angle of 75 degrees?thrust fault.Our results show that the seismic moment release was 7.49×10¹⁸ N·m,corresponding to a moment magnitude of Mw6.55.The maximum slip was 1.03 m and the main rupture zone extended to a 12 km depth.The earthquake may have been related to the release of strain accumulated during the subduction of the Indian plate beneath the Eurasian continent.We identified a high strain rate and low b-values around the epicentral area before the earthquake,indicating that the earthquake was nucleated under a high strain/stress state.The data indicate two regions,southwest and southeast to the epicenter?the eastern Main Himalaya Thrust and northern end of the Sagaing fault?,which remain under high stress/strain conditions and pose a significant seismic hazard.?2?In this study,we utilize the interseismic GPS velocity and construct the fault kinematic model in the framework of Bayesian approach using Markov Chain Monte Carlo?MCMC?method,so that to figure out the interseismic creeping/locking along the Elashan fault.The results demonstrate that the locking depth of the Elashan fault is?15 km,and the deep slip rate is 5.0±1.5 mm/a,i.e.,a rate of relative motion between the two blocks at the two sides of the fault.Despite GPS stations are sparse,they provide the resolution of along-strike variations in slip rate.The middle segment with locking coefficients of 0.6?0.7 appears to be strongly locked due to the changes of fault geometry,thus acting as an asperity.The northern and southern segments are characterized by creeping or mild locking,with locking coefficients of0.2?0.3.The equivalent seismic moment accumulation rate on the asperity is2.35×10¹⁷ N?m/a,which is equivalent to an Mw 5.6 earthquake.Regarding the sparse coverage of the current GPS network,we propose locations for deploying new GPS stations with limited budget based on the rule of minimizing the fault slip uncertainty.