Rupture Model And Stress-triggering Relationship Of The 2020 Elaz(?)(?) Mw 6.8 Earthquake In Turkey

Accurately quantifying the rupture model of an earthquake is the basis for studying the causes of earthquakes,rupture dynamics,and exploring the structure of active faults.It can greatly help understand how stress accumulates and releases in the seismic cycle of the fault zone,and provide guarantee for the evaluation of the potential earthquake risk.In this study,a Bayesian probabilistic inversion method of source parameters was developed,and considering observation error,simulation error and model prior information,the uncertainty of source parameters was well quantified.In addition,the Bayesian probabilistic inversion method was successfully applied to the study of the rupture model of the Elaz(?)(?)earthquake in Turkey on January 24,2020.The January 24,2020 Elaz(?)(?) earthquake in Turkey was the most severe and destructive earthquake around the East Anatolian Fault Zone(EAFZ)since the Ms6.9 Bing?l earthquake on May 22,1971.The seismogenic fault segment(Puturge),has not ruptured recently and was considered a seismic gap prior to the 2020earthquake sequence.In this paper,the co-seismic deformation field of the 2020Elaz(?)(?)earthquake is obtained by using the Sentinel-1 satellite In SAR data automatic processing system(Li CSAR).The results show that there are two main deformation regions,which is concentrated in the range of?60 km long and?40 km wide,and the largest line-of-sight deformation is 28.30 cm observed in the ascending orbit116A image.Based on the Bayesian probabilistic inversion algorithm of seismic source parameters,the maximum posterior probability parameter solution and 95%confidence interval of the fault dislocation model are obtained.The results show that the slip of the seismogenic fault is dominated by sinistral strike-slip,the optimal rake angle is-3.7°,the strike is approximately NE-SW direction,and the optimal dip angle is 68.8°which dips to northwest.The length of the seismogenic fault ranges from 34.662 to 37.760 km,the width from 16.364 to 19.994 km,and the slip range is from 0.787 to 0.985 m.Combined with GNSS and In SAR data,the slip distribution on the fault plane was well constrained.The results show that the length of slip along the strike is?50 km,mainly concentrated in the depth range of 2.0?17.6 km.The slip has not reached the surface,and there is obvious shallow slip deficit.The inverted average slip is 0.43 m,and the average rake angle is-0.3°.The maximum slip is 1.32 m,located at a depth of 9.0 km,which is just located at the southwest of the AFAD hypocenter and almost at the same depth as the GCMT and KOERI hypocenters.The calculated seismic moment is 1.93?10¹⁹Nm,which is equivalent to the moment magnitude Mw 6.82.The spatial distribution characteristics of the aftershocks relocated within three months after the mainshock were also analyzed.The aftershocks have a span of?75km in the strike direction N242°E and a depth range of 5-20 km.The distribution of the aftershocks deepens slightly along the direction of strike to the northeast.In this study,we analyze the Coulomb stress change caused by the co-seismic rupture and viscoelastic relaxation effect of 17 typical strong earthquakes with magnitude 6 or above since 1822,and discusses the stress triggering relationship between it and the 2020 Elaz(?)(?)earthquake.The results show that the Coulomb stress change caused by the co-seismic rupture of 1874(M 7.1),1875(M 6.7),1893(M 7.1),1905(Ms 6.8)and 1939(Ms 7.8)earthquakes promotes the rupture of the 2020 Elaz(?)(?)earthquake.The magnitude of the post-earthquake viscoelastic effect is smaller than the Coulomb stress change caused by the co-seismic rupture,and the effect of Coulomb stress is closely related to the magnitude and distance to the 2020 Elaz(?)(?)earthquake.The interactive triggering process of earthquakes of M6 and above at the East Anatolian fault zone since 1822 is also analyzed,and the relationship between cumulative Coulomb stress changes and strong earthquakes is discussed.The results showed that 1872(M 7.2),1875(Ms 6.7),1905(Ms 6.8),1924(Ms 6.8)and 1939(Ms7.8)earthquakes were obviously promoted by the previous earthquake ruptures,and the 1939(Ms 7.8)earthquake also had a significant inhibitory effect on the subsequent earthquake rupture.