Coseismic Deformation Monitoring By InSAR And Fault Dislocation Inversion

As a rapidly developing space geodetic technology in recent years,InSAR provides an advanced method for monitoring the ground deformation,especially the coseismic deformation.Due to the advantages of high automation and low cost,InSAR technology can also extract high-precision deformation of the earth's surface from observations with continuous spatial coverage without the ground control points.On October 17,2016?15:14?,an Mw5.9 earthquake occurred in Zaduo County,Qinghai Province?epicenter:32.81°N,94.93°E?.Besides,on November 25,2016?14:24 UTC?,an Mw 6.6 earthquake occurred in Aketao county of Xinjiang Uygur Autonomous Region?epicenter:39.27°N,74.04°E?.The two seismogenic regions are located in high-altitude,remote and inaccessible areas,where sufficient ground measurement data are not available.Therefore,for studying the coseismic deformation triggered by the Zaduo and Aketao earthquakes,InSAR technology is an ideal method because of its advantages.In this paper,based on the SAR data provided by the ESA Sentinel-1 satellite,GMTSAR program were used for differential interferometry?D-InSAR?processing.The coseismic deformation fields following Zaduo and Aketao earthquakes were obtained by D-InSAR processing.Here,the Okada half-space elastic dislocation model and the Steepest Decent Method?SDM?program were used to simulate the seismic deformation field.The optimal source model is obtained by changing the fault's parameters.Finally,the tectonic mechanism and causes of the two earthquakes were analyzed based on the inversion results of source models and fault parameters combined with the geological settings and historical seismic data.According to the coseismic deformation result of Zaduo earthquake,the fault upper plate with elliptic deformation is located at the southeast side.The maximum amount of deformation is about 5 cm.The fault parameters results of Zaduo earthquake shows that the rupture center was located at?32.86°N,94.86°E?and depth of⁸ km.The rupture plane is about 30 km along strike and 30 km along dip,and it has an average strike of59.83°SE and a dip of 67°S.The maximum amount of slip is about 0.18 m and the average amount of slip is about 0.04 m.The estimated seismic moment is 1.08×10¹⁸N·m and the corresponding moment magnitude is Mw5.9.This event belongs to a normal fault with sinistral strike-slip component.The slip of the fault is mainly distributed at the depth of 5-20 km,which indicates that zaduo earthquake belongs to the shallow earthquake.Many seismic activities related to the developed normal faults with tensile structure occured in the inner part of the Qiangtang block.The Zaduo earthquake may relate to these tectonic settings of the Qiangtang block.According to the coseismic deformation field,the rupture length of Aketao earthquake is nearly 70 km.There are two elliptic deformation areas in the southern side of the fault.The maximum amount of deformation is about 20 cm.The inversion result shows that the rupture center was located at?39.17°N,74.38°E?.The rupture plane is about 68 km along strike and 40 km along dip,and it has an average strike of 105.2°SE and a dip of 76.0°S.The average amount of slip is about 0.16 m and the maximum amount of slip is about 0.59 m.The estimated seismic moment is 1.31×10¹99 N·m and the corresponding moment magnitude is Mw6.68.Both the inversion result and the geological survey indicate that aketao earthquake is a dextral strike-slip event with double fracture.The dislocation is mainly distributed at the depth of 5-22 km,which indicates that this earthquake is a shallow earthquake.The seismogenic Muji fault lies on the northern edge of the Muji basin,which extends over 100 km at the southern foot of the Kunrgai Mountains.The nearly EW-trending tensor at north part of the Konger tensor system was aborbed by the dextral strike-slip movement of the Muji fault.Due to little amount of slip between the two fractures of Aketao earthquake,there is a risk of fault rupture which may trigger an earthquake in future.