Three Dimensional Co-seismic Deformation And Fault Slip Of Maduo Mw 7.4 Earthquake By Jointing InSAR And GNSS Observation

In recent years,the rapid development of geodetic techniques(GNSS,leveling,InSAR,gravimetry)has improved the accuracy of crustal deformation monitoring,and the monitoring results(including vertical and horizontal displacements)provide strong evidence of seismic source parameters and fault activity for earthquake prediction.Synthetic aperture radar(InSAR)technology,as an important technical means of earth observation,has improved the effectiveness of traditional seismic deformation monitoring methods(such as level and GNSS)due to its high spatial resolution and all-weather observation characteristics.However,as the deformation acquired by InSAR has the problem of line-of-sight orientation blurring,combining it with GNSS data to monitor the real three-dimensional deformation of the ground surface provides a more effective basis for seismic activity research The combination of InSAR and GNSS data provides a more effective basis for seismic activity studies.An earthquake of magnitude Mw7.4 occurred on 22 May 2021 in Mado County,Qinghai Province.The earthquake occurred on the Kunlun Pass-Jiangcuo fault zone within the QinghaiTibet Plateau.The study of the source geometry parameters and fault slip distribution of this earthquake is of great theoretical value for understanding the seismogenic characteristics of earthquakes within the Qinghai-Tibet Plateau and the regional tectonic pattern of the region.In this paper,the three-dimensional surface deformation around the earthquake is obtained by combining InSAR and GNSS observations.At the same time,the sliding distribution of strikeslip and dip-slip on the fault plane is inverted based on the half-space elastic medium dislocation model and the Earth’s stratified medium model dislocation model using GNSS data,InSAR data and joint GNSS-InSAR observations.The following conclusions were obtained:1.Based onSentinel-1 data,the synoptic deformation field of the Mado earthquake lift track was obtained.The main area of deformation caused by the earthquake is approximately200 km × 70 km,divided into two deformation areas in the south and north,and the synoptic rupture to the surface.The maximum upward deformation in the LOS direction is about 1.5 m and 0.8 m,and the maximum downward deformation is about 1.2 m and 0.8 m.The results of the GNSS solution show that the fault is moving westward with a horizontal deformation component of about 1.2 m for the NE disk and 0.7 m for the SW disk,which have the same characteristics as the InSAR deformation field.The results of the deformation field indicate that the fault is mainly moving horizontally and is consistent with the motion of left-slip.2.Based on the joint solution model using the least squares method for algorithm optimization,the final three-dimensional isoseismic deformation of the N-S,E-W and U-D components of the Mw7.4 earthquake in Mado was obtained.The three-dimensional isoseismic deformation fields have the same spatial characteristics as the LOS of InSAR through comparative analysis,and the deformation amplitude in the E-W region is much larger than that in the N-S and U-D regions.The combined InSAR and GNSS synoptic deformation fields show that the Mado earthquake fault trace is essentially the same and clearly located,with the fault trending towards NWW and tending towards NE with a length of about 200 km.this conclusion confirms that the Kunlun Pass-Jiangcuo fault is the seismic fault that generated the rupture of this earthquake.3.Based on the distributed slip model,isoseismic slip distribution calculations are performed using SDM in semi-infinite spatially elastic media and multilayer media of the Earth.Combining the inversion results from GNSS,InSAR and combined GNSS-InSAR data,the main rupture range of the fault slip distribution is at a depth of 10-16 km below ground and is approximately 150 km long along strike.the average slip for the Mado Mw7.4 earthquake was5-6 m.The average dip slip at local locations reached the slip level and the fault strike was approximately 267°.The average slip angle is about 83°.The inversion results based on the semiinfinite space elastic medium model yielded moment magnitude Mw7.5,and the inversion results based on the Earth multilayer medium model yielded moment magnitude Mw7.6.The magnitude of the semi-infinite space elastic medium model inversion is closer to the GCMT value,which is more effective.In the semi-infinite space elastic medium and the Earth multilayer medium,the elastic parameters are different and the deformation of the Earth layered model can be divided into elastic and inelastic parts,and these differences will have some influence on the model calculation results.Overall the inversion results are in better agreement with the seismological results.