Abstract: Three-dimensional seismic deformation field is of great significance to the study of earthquake mechanism. It has been successfully reconstructed for only moderate or strong earthquakes in previous research. For small and medium earthquakes, the reconstruction of three-dimensional deformation field is vulnerable to noise and other effects, due to the small magnitude of displacement, and the large uncertainty in InSAR’s azimuthal deformation. Taking the May 22, 2016 Dingri M_W5.3 earthquake as an example, we attempt to reconstruct its three-dimensional deformation field. Firstly, the coseismic deformation field of the earthquake is obtained by using InSAR technology under the ascending and descending observation mode of Sentinel-1. According to the characteristics of coseismic deformation field, regional structure and so on, the three-dimensional deformation field of co-seismic is reconstructed by adding a limited equation (strike-slip motion is 0) in it. The results show that: the subsidence mainly distributes near the epicenter with the maximum amplitude reaching 7 cm, and the deformation in the north-south direction is small (about 2 mm), while accompanied by a horizontal westward motion of 2 cm; small eastward motions (1.5 cm) occur in the west and east parts of the deformation center region. From the deformation characteristics, the earthquake is illustrated as normal fault movement. In view of the characteristics of the seismic deformation field, a more suitable resampling point selection method based on continuous stratified sampling is proposed in this paper. Taking down-sample from the LOS displacement field and the reconstructed three-dimensional deformation field, the slip distribution on the fault plane is obtained, and the results from two data are similar. The best strike of the fault is about 181°, the optimal dip angle of the seismogenic fault about 45°, the average slip direction of the fault dislocation being about -87.1°, and the average slip is 3.6 cm. The maximum slip is located at a depth of 6.5 km. The observed fault slip is equivalent to an earthquake with a moment magnitude of M_W5.4.

Key words: Three-dimensional Deformation Field Reconstruction, InSAR, Continuous stratified sampling, Inversion, Small and Medium Earthquakes