| Unlike large earthquakes,which typically occur along large active faults on the surface,some earthquakes are not controlled by surface active faults and do not rupture on the surface,such earthquakes generally occur on blind faults several kilometers deep below the young fold belt,and such earthquakes are called blind thrust earthquakes.The surface deformation caused by this kind of earthquake is small,and it is difficult to record the observation by ordinary observation methods.With the development of Interferometric Synthetic Aperture Radar(InSAR)technology,it has been widely used in the field of seismic deformation monitoring by virtue of its characteristics of all-weather,all-time and high-precision surface deformation information with high spatial resolution.A 6.2-magnitude earthquake struck near Hutubi county,Changji prefecture,northwest China's Xinjiang Uygur autonomous region,on Dec 8,2016,the earthquake was a typical blind fault event.In this paper,the scientific problem of unclear seismogenic fault of Hutubi earthquake was analyzed,and the source parameters were inversed based on elastic half-space dislocation model.The seismogenic fault was further constrained by relocation data of aftershocks,seismic profile data and regional geological structure.At the same time,the stress change triggered by Hutubi earthquake was calculated and the future seismic hazard in this area was analyzed.The work of this paper adds a new example for the study of tectonic activity in the north Tian Shan area,and provides some basis for the study of medium and long-term seismic risk in this area.The main work and conclusions are as follows:(1)Sentinel-1 radar images wer e used to obtain the coseismic deformation field of Hutubi earthquake in 2016.The results showed that the coseismic deformation mainly occurred near the Junggar Southern Fault(JSF).The surface deformation caused by the earthquake is small and the rupture does not extend to the surface.The maximum line of sight deformation of T014 A in the ascending orbit is 22 mm,and the maximum line of sight deformation of T094 D in the descending orbit is 20 mm.(2)Based on the elastic dislocation model,the multi-peak particle swarm optimization(MPSO)algorithm was used to determine the geometric parameters of the fault,including strike,dip,rake,fault length,fault width,location and depth,with the coseismic deformation obtained from InSAR data as the constraint.Based on the inversion results,two models of north dipping and south dipping were established.The strike,dip and rake of north dipping model are 270 °,57 ° and 93 °,and 87 °,29 ° and 85 ° of the south dipping model.(3)We determined the distributed slip on the fault surface through linear inversion based on the optimized geometric parameters of the fault.The results showed that the fault rupture did not reach the surface,and the main slip momentum of the north dipping model was located at a depth of 12-17 km with a maximum slip momentum of 56 cm.The main slip momentum of the south dipping model was located at a depth of 13-16 km with a maximum slip momentum of 47 cm.(4)According to the results of relocated aftershocks and artificial seismic data,the tendency and structure of seismogenic faults are analyzed.We concluded that the seismogenic structure of the Hutubi earthquake was connected to the HMT fault at a depth of 16 km,which was a recoil structure on the HMT fault.(5)Based on the coseismic slip distribution,the regional stress changes caused by the event were studied.The results show that the increase of coulomb stress is mainly concentrated in the upper half of the fault.Combined with the structure around the source area,we analyzed the potential seismic risk in this area,and concluded that although the Hutubi earthquake increased the coulomb stress(about 0.2mpa)in the upper half of the fault,it is unlikely to have a major earthquake of magnitude 6 or above in this area due to geological structure. |
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