Research On Deformation And Coulomb Stress Of Aketao M_w6.6 Earthquake Based On Sentinel Data

The occurrence of large earthquakes often brings huge disasters to human beings,and at the same time,it will induce secondary disasters such as landslides,debris flows,floods,etc.Fault activity is closely related to earthquake occurrence.The study of fault geometry,slip distribution and Coulomb stress can provide basic data and scientific basis for the work of earthquake prevention and disaster reduction.At 22:24 on November 25,2016,Beijing time,a Mw6.6 earthquake occurred on the NWW-trending Muji Fault in Aketao Region,Xinjiang,which caused certain losses to local people's property.For the Aketao Mw6.6 earthquake,this paper obtains the deformation field information caused by the earthquake based on Sentinel data,confirms the formation of two deformation centers on the surface;and uses the data as constraints to invert the geometric model of the fault;and explores The slip distribution of a single fault,the inversion results show that the earthquake may contain two seismic events,so the dual fault slip distribution was inverted.Finally,the regional Coulomb stress change was calculated,and the risk of the earthquake was judged.The main research work and conclusions are as follows:(1)This paper uses D-InSAR technology to obtain the LOS-direction deformation fields of the coseismic ascending and descending orbits,and the results of the two orbits can reflect the surface deformation caused by the earthquake.In the deformation field of the descending track,there are two settlement centers on the south side of the Muji fault.The peak value of the west settlement is?14cm,and the peak value of the east settlement is?23cm.In the deformation field of the ascending orbit,it is found that there are two uplift centers on the south side of the Muji fault,and the deformation values of the east and west uplift centers are both?12.5cm.Taking the deformation fields of the above two orbits as constraints,the Bayesian method is used to inverse the geometric parameters of a single fault model,where the strike is 106.9°,the dip is 73.8°,and the focal depth is 17.35km;on the basis of the single fault model,construct A dual-fault model with different dip angles.The dip angles of fault I and fault II are 70.79° and 55.33°,respectively.(2)This paper uses SDM to invert the coseismic slip distribution of faults based on a single fault model and a double fault model.Under a single fault model,the inversion results show that the fault is a strike-slip fault,and there are two slip peaks on the fault plane.The maximum slip is 0.66m on the west side of the fault and the depth is 11.7km;the largest one is on the east side of the fault.The amount of sliding is 0.83m and the depth is 7.5km.The maximum fitting residual of the inversion result is?5cm,and the seismic moment is MW6.65.Under the dual-fault geometry model,fault I is a strike-slip fault,the maximum slip of the fault plane is?0.68m,and the depth is?11.61km;the nature of fault II is mainly strike-slip and normal fault,and the maximum slip of the fault plane is?0.77m,the depth of the sliding peak is?7.46km,the maximum fitting residual of the inversion result is?3cm,and the total moment magnitude is Mw6.62.From the overall results,the slip distribution results inverted by the single-fault model and the double-fault model have high consistency,but the maximum slip magnitude is slightly different.Compared with the slip distribution of the single-fault model,the slip of the dual-fault model increases at fault I and decreases at fault II.The maximum fitting residual value of the inversion result is reduced by?2cm.It can be seen that the dual-fault model can Better simulation of fault structure.(3)Based on the slip distribution model of single fault structure and double fault structure,the Coulomb stress change of the optimal fracture surface was calculated,and the aftershock information within 24 hours was displayed on the Coulomb stress change map,and it was found that the calculation occurred in two models.The probability of the enhanced Coulomb stress area is above 60%.According to statistics,From 0:00 on December 1,2016 to 24:00 on November 30,2020,nearly 86 earthquakes of magnitude 3 occurred in the region.Among them,under the condition of the slip distribution model of a single fault structure,the probability of being located in the enhanced Coulomb stress area is?44%;under the condition of the sliding distribution model of the double fault structure,the probability of being located in the enhanced Coulomb stress area is?57%.It is proved that the Coulomb stress change calculated by the dual-fault model is closer to the actual distribution of aftershocks than the single-fault model.And found that when the Coulomb stress change is positive,it is easy to cause earthquakes.The Coulomb stress of the Aketao earthquake is in an increasing state,and there are still many earthquakes before and after the earthquake.It can be seen that the activity in this area is quite active,and it cannot be ruled out that earthquakes may still occur in this area in the future.Based on 28 scenes of ascending orbit data one year after the earthquake,SBAS-InSAR technology was used to obtain post-earthquake deformation information.The results show that the post-earthquake deformation trend is relatively consistent with the coseismic deformation trend.The area south of the fault is mainly uplifted,but the magnitude is greatly reduced,and the LOS uplift is up to?3.0cm.