## 3 Numerical Experiments
### Imaging Results
#### 3.2.2 Layer Models  
The imaging results of model B-1 are shown in Figure 13. In the MVSS beamforming imaging result (Figure 13b), two interfaces can be clearly observed. There is some light interference on both sides of the image (Mark 2) and between the interfaces (Mark 1). Furthermore, some parts of the deeper interface are missing (Mark 3). In the Kirchhoff migration imaging result (Figure 13c), the interfaces between the layers can be observed clearly, but artifacts appear between the two layers and on both sides of the image (Mark 1), and some arc-shaped interferences can be observed on both sides of the image (Mark 2). The DAS beamforming imaging result is shown in Figure 13d; the interfaces can be observed, but arc-shaped interferences and a massive surface wave artifact at the top of the image can also be observed. Figure 12: Model A-3. (**a**) True velocity model. (**b**) Imaging result of MVSS beamforming. (**c**) Imaging result of Kirchhoff migration. (**d**) Imaging result of DAS beamforming. Comparing the three imaging methods reveals interferences between the different interfaces in the Kirchhoff migration and DAS beamforming imaging results. In the MVSS beamforming image, the amplitude of the surface wave artifact is weak, and the interferences between the interfaces are suppressed. The thickness of the interface between the two layers is approximately 0.4 m. The best resolution given the wavelength of the wavelet is 0.24 m. In contrast, the interfaces are thicker (approximately 1.6 m on the deeper interface) in the Kirchhoff migration and DAS beamforming images, which means that the vertical resolution of MVSS is higher in this layer model. However, artifacts caused by the superposition of S-wave energy still exist and caused interference between the interfaces. Kirchhoff migration and DAS beamforming suffer from similar intersecting interferences (Mark 4) caused by S-waves. However, at shallow depths, these intersecting interferences are replaced by vertical bars in the Kirchhoff migration image. Compared with the MVSS beamforming imaging results obtained for the cave models, the interfaces can be readily determined, but the amplitudes of the interfaces in this layer model seem weaker than the amplitudes of those in the cave models (using the same imaging and display parameters in every model). In addition, the layers are missing on two sides of the image because the shots range horizontally from 5 m to 25 m.  
The imaging results of model B-2 are shown in Figure 14. Figure 14b shows the imaging result of MVSS beamforming. The interfaces between the layers can be observed, and the location of a fault can be inferred from the shapes of the interfaces, but the details of the fault are difficult to discern. Lightly surface wave artifact can be observed (Mark 1).Dislocations in the shallow interface can be observed. For the deeper interface, although the upper and lower stratigraphic boundaries can be seen, the dislocations cannot. Slight interferences can be observed on the sides of the image and beneath the interface (Mark 2). Figure 14c shows the imaging result of Kirchhoff migration. The artifact caused by surface waves can be observed at the top of the image. At the same time, interferences can be observed above the shallower interface and beneath the deeper interface. Figure 13: Model B-1. (**a**) True velocity model. (**b**) Imaging result of MVSS beamforming. (**c**) Imaging result of Kirchhoff migration. (**d**) Imaging result of DAS beamforming. Figure 14d shows the imaging result of DAS beamforming. Likewise, the artifact caused by surface waves can be observed at the top of the image (Mark 1). In addition, artifacts caused by S-waves are present on both sides of the image. We also detected interferences between the two interfaces and beneath the deeper interface. The interferences above the shallower interface appear with different shapes in the Kirchhoff migration and DAS beamforming imaging results (Mark 3).