## 3 Model Validation and Comparison
### Model Validation  
In this study, the Splash3D model is coupled with the Bingham model to simulate the slump-type landslide tsunamis. The slump is modeled as a Bingham fluid. The validations are made in terms of free-surface and slump shape. The comparisons of simulated surface elevations at t = 0.4 s and t = 0.8 s are displayed in Figure 5 along with the experimental data ([PERSON] [16]) and numerical results from NASA-VOF2D ([PERSON] [16]), NHWAVE (Ma [53]), and Fluidity ([PERSON] [10]). As observed in Figure 5, the result from NASA-VOF2D-Bingham is closer to the laboratory data than that from NASA-VOF2D-ideal. The wave excited by the idealized slump is bigger than that excited by Bingham slump. The slump deforms freely while it is idealized. However, the yield stress in the Bingham slump restricts the deformation at the initial stage of the sliding process. NHWAVE over-predicts the surface wave generated by the submarine slump. NHWAVE (blue line) over-predicts the surface waves generated by the underwater slump. The reason might be that the free surface movement is controlled by the depth-integrated continuity equations. Although the governing equations are the Navier-Stokes type, the depth-integrated process will average out the effect of vertical acceleration and vortex. [PERSON] [10] provided three wave results from three approaches which are nearly identical. The green line presented in Figure 5 is the averaged results of them. It is not surprising that the Fluidity result is equivalent to the NASA-VOF2D-ideal result. The foundation of these models are similar, which is use the sediment transport theory without considering the rheological behaviors to simulate landslide. Figure 5: A comparison of free-surface elevations of four numerical models: Splash3D (red lines—different lines indicate different resolutions with dx = dz = 4.35–6.25 mm, Fluidity from [PERSON] (blue lines), non-hydrostatic wave (NHWAVE) from [PERSON] (green lines), NASA-VOF2D from [PERSON] (black lines—the solid line is the ideal model result, the dashed line is the [PERSON] model result), and the experimental result from [PERSON] [16] (black dot) at (**a**) t = 0.4 s and (**b**) t = 0.8 s.  
The accurate results of slump-induced waves are given by Spash3D with considering the rheological properties of landslide. Different red lines present different resolution results, in which grid size (dx = dz) varies in the interval 4.35-6.25 mm. In both panels (a) and (b), the differences between four different resolution results are less than 2% in terms of the wave amplitude. This indicates that the solution has converged when the grid size is less than 6.25 mm. To obtain accurate results, however, the grid size dx = dz = 4.35 mm is used to simulate all of the cases in this study. The Splash3D results match well with experimental data of [PERSON] [16] at both time intervals, which means that more accurate simulation of the underwater slump would require a more thorough consideration of the rheological behavior of the slide material. As for the comparisons of the slump shape, Part I [42] presents the 3D validation of the slump slide on the dry land for the detailed comparisons and discussions on the rheology parameters. In Part II, the simulated results are compared with the laboratory data as shown in Figure 2 at t = 0.4 s and 0.8 s. The simulated slump shape is very close to the laboratory data at t = 0.4 s. This indicates that the yield stress of the slump suggested by [PERSON] [16] performs very well at the initial stage of the slump slide. The difference between the simulated result and the laboratory data is slightly larger at t = 0.8 s. However, the simulated moving distance is nearly identical to the laboratory data. The simulated thickness of the slump is similar to the laboratory data in the front area around (x, z) = (-1.1, -1.1) at t = 0.8 s. The role of the slump front is to push away the ambient water for generating the water waves.