## 1 Introduction  
The seismic response study of landslides generally focuses on the study of the dynamic stability of landslides. The pseudo-static, numerical simulation, physical simulation,Newmark method and probabilistic method are the main analytical methods used [1; 2; 3; 4; 5; 6; 7; 8; 9; 10]. The principle of the pseudo-static method is simple, but it fails to consider the spectral characteristics of ground shaking and the effect of holding time [11; 12]. Numerical and physical simulations can adopt the actual ground shaking to reproduce the dynamic response characteristics and damage process of slopes more realistically, but it is difficult to establish accurate models for slopes with complex geological conditions [13].  
The Newmark method is a stability analysis method for dams that was proposed in 1965 [14], which is widely used because of its calculation simplicity. The method has undergone continuous refinement and improvement, from only considering the initial rigid block model to the fully coupled models [15], from only considering horizontal seismic acceleration to considering three-way seismic acceleration [16; 17], and from only considering the constant shear strength parameters of the sliding surface to considering the dynamic parameters that are dependent on shear displacement [18]. Some scholars have tried to also consider the vertical seismic acceleration as a pseudo-static equivalent loading to participate in the solution of yield acceleration, but it caused great errors in the case of near-fault slopes with a large vertical component.  
The vertical earthquake component's influence on the degree on seismic stability and slip deformation of geotechnical buildings has been discussed, and it is thought to have an important impact on the strength variations in structures [19; 20]. Research has shown that the vertical component of an earthquake increases the nonlinear vertical displacement and the demand/capacity ratio in masonry structures [21; 22]. It has been reported that the vertical component of an earthquake leads to a significant rise in the axial force in the central columns and even a collapse of the underground structures [23; 24]. The variational mode decomposition technique is employed to show that the maximum displacement of elastomeric bearings subjected to a pulse-like horizontal ground motion is moderately amplified, on average, when the vertical excitation is also pulse-like [25]. The Daguangba landslide was the largest landslide that was triggered by the Wenchuan earthquake and also a globally rare giant landslide. The earthquake records at the nearest Qingping seismograph station (51 MZQ) show that the landslide area not only suffered strong horizontal seismic motion (0.824 g), but also received almost equal vertical seismic motion (0.8 g). However, only the horizontal ground motion is considered, and the vertical ground motion is ignored when using the Newmark method [26; 27; 28], so the improved Newmark method, which considers the direction of the vertical sliding surface, is used to calculate the permanent displacements of the Daguangbao (DGB) landslide. The hypothesis was that the vertical acceleration and horizontal inertia force increased the possibility of landslide instability. This can be due to the increase in the permanent displacement under vertical seismic acceleration, which can help to analyze the instability time of the Daguangbao landslide.