Research On The Full-period Deformation And Source Parameter Inversion Of The 2016 Menyuan M_w5.9 Earthquake Based On InSAR Technology

The earthquake is mainly caused by the dislocation of the seismo-generating fault,which releases large energy,occurs at a fast speed,and has a strong destructive power,causing great harm to the safety of people's lives and property.On January 21,2016,the MW5.9 earthquake occurred in Menyuan,Qinghai Province,China.Although the magnitude of the earthquake was small,it occurred in the northeastern margin of the Qinghai-Tibet Plateau,a belt of frequent medium-strong earthquakes in China.In addition,there have been two moderate and strong earthquakes(Mw6.0 Menyuan earthquake in 1986)in almost the same tectonic position in this region in just 30 years.This paper focuses on how to quantitatively determine the source parameters of the Menyuan earthquake in 2016,obtain the influence of the main earthquake on the surrounding area and the deformation status after the regional earthquake,and then discuss the relationship between the 1986 Menyuan earthquake and this earthquake.The Sentinel-1 ascending and descending data are used to obtain the full-period surface deformation of the 2016 Menyuan earthquake.The source parameters of the earthquake are determined by using the "two-step" inversion with the constraint of coseismic observation deformation.Finally,combining with the regional geological structure,the results of two-dimensional(2D)deformation,coseismic CFS and its influence on the surrounding faults are analyzed,and the triggering effect of the 1986 Menyuan earthquake on the earthquake is quantitatively discussed.The results have important meaning for understanding the characteristics of seismogenic faults and evaluating the seismicity risk in the northeastern margin of QinghaiTibet.The main results and innovations of this paper are as follows:1.Based on the D-InSAR technology to obtain the coseismic deformation field of the Menyuan earthquake,the ascending and descending orbit results show that the Menyuan earthquake occurred on the north side of the Menyuan area.As a result of the two orbits,only the uplift deformation of the surface are observed,and the shapes are all elliptical,extending in the NW-SE direction.The profile results show that this fault movement did not damage the surface.Combining the results of the coseismic ascending and descending orbit of the Menyuan earthquake,the 2D deformation shows that the vertical deformation is uplifting,and the eastwest deformation is mainly eastward.It shows that the seismogenic fault is a dipping sinistral thrust fault.2.Based on the results of InSAR observations and the use of "two-step" inversion,the source parameters of this earthquake were obtained.The results showed that the seismogenic fault is a concomitant buried reverse fault in the northeastern part of the Northern Lenglongling Fault with a thrusting left-lateral movement,which is a SW dipping sinistral thrust fault with a strike angle of 140°.The fault slip of this earthquake is mainly distributed at 5-18km underground,and the maximum slip is 0.47m.The seismic moment is 1.0*1018N·m,and the magnitude of the moment is Mw5.93.3.PS-InSAR technology is used to obtain the post-seismic deformation rate.In order to better show the vector of spatial deformation,the MSBAS-InSAR technology is used to decompose the results in 2D deformation.After the earthquake,obvious creep slip occurred in the gate source area.The vertical maximum cumulative sliding amount was ± 15mm,and the east-west maximum cumulative sliding amount was ± 17mm.Compared with the coseismic results,the after-slip impact range after the earthquake is similar to that of the coseism.It is mainly at the junction of the northwest side of the Lenglongling Fault and the Northern Lenglongling Fault.The ground surface is gradually stable after six months of the main shock.4.Based on the comprehensive analysis of the CFS results and the distribution of aftershocks,the CFS distribution caused by the 2016 earthquake is in good agreement with the distribution of aftershocks.The earthquake caused stress loading on the southwest of the western segment of the Lenglongling Fault and on the southeast of the eastern segment of the Northern Lenglongling Fault,as well as along these two faults.The 2016 Menyuan earthquake was located in the 1986 Coulomb force loading area.Based on the seismic stress triggering theory combined with structural dynamics analysis,it is speculated that the earthquake in the last century had a certain propelling effect on the occurrence of this earthquake.