## 4 Slip Model Inversion
### Distribution Slip Inversion  
Based on the geometric parameters of the fault determined by nonlinear inversion, the fault plane was divided into uniform and continuous rectangular sub-units to obtain the fine slip distribution on the fault plane. When the geometric parameters of the fault were determined, the motion parameters on the fault plane and the surface deformation were transformed into a generally linear relationship. The linear model of the parameters of the slip distribution and the deformation and displacement of the ground was related to [PERSON]'s function matrix. After determining the parameters of the fault geometry model by nonlinear inversion, the fault plane was divided into uniform and continuous rectangular sub-units, and the slip amount of each sub-unit was solved separately; the ground deformation and displacement caused by the strike-slip and tilt-slip of each sub-unit constituted the [PERSON]'s function matrix. In this paper, the length and width of the fault plane were extended to 30 km and 20 km along the strike and downdip directions and were divided into rectangular units of 1 km \(\times\) 1 km, and a total of 600 units were obtained. Consistent with the uniform slip inversion, the Okada uniform elastic half-space dislocation model was used to simulate the surface deformation field. In the inversion process, in order to avoid the oscillation of the sliding distribution solution, a Laplace smoothing constraint was added to obtain a reliable and stable solution:  
\[F(m)=\|d-Gm\|^{2}+\kappa^{2}\|Hm\|^{2} \tag{2}\]  
where \(\kappa^{2}\) is the smoothing factor, \(H\) is a Laplacian, and \(\|Hm\|^{2}\) is the slip roughness. The fault slip distribution model is shown in Figure 4. The predominant slip mainly occurred along the fault at the depth of 1-14 km, the peak slip was able to approach 0.6 m, which is at the depth of 5 km, and the results showed that the coseismic rupture did not extend to the surface. The results indicate that the fault model had a dip angle of 76.2\({}^{\circ}\) and an average slip angle of \(-\)176.3\({}^{\circ}\), which is consistent with the focal mechanism solution  
Figure 3: Deformation field down-sampling results of ascending and descending: (**a**) the ascending deformation field down-sampling result; (**b**) the descending deformation field down-sampling result. given by USGS, and it belongs to the dextral strike-slip earthquake, as represented in Table 2. In order to verify the reliability of the above fault model, the residual error between the simulated deformation and the real deformation was calculated based on the Okada model, and Figure 5 shows the simulated deformations and residuals for the slip model. From the overall perspective, the simulated deformation field was similar to the shape and size of the deformation field obtained by InSAR observation. Figure 5c,d shows that the standard deviations of the ascending and descending data were about 3 cm, which shows that the simulated deformation had a good fit with the real observation, and the fault geometry model obtained by the inversion can better explain the surface deformation of the Yangbi earthquake. In other words, it can be reasonably concluded that the general cooseismic displacement obtained by the Sentinel-1A satellite can be accurately reproduced by the best slip distribution model.