## 1 Introduction  
With the expansion of human activities and the intensification of global climate change, landslide geological hazards are occurring with increasing frequency, causing serious economic losses and casualties. China is one of the regions with the highest number of landslide incidents, and to date, thousands of landslide hazards still occur annually, causing hundreds of deaths and billions of USD (United States dollar) of economic losses, and the hazard prevention and mitigation situation remains severe [1]. Deformation monitoring is an essential means for the active prevention and control of landslide hazards, and with the rapid development of computer technology and geomaticscience and technology, novel monitoring technologies such as GNSS, InSAR, and UAV vision have made positive contributions to landslide hazard monitoring and early warning systems [2; 3; 4]. Generally, InSAR and UAV are employed for landslide early identification and detection over large areas, because of their high spatial resolutions. The authors of [5] investigated the spatial and temporal evolution characteristics of a landslide before and after damage with InSAR, UAV, and remote sensing, and found that InSAR and remote sensing could be used for the early identification of unstable slopes. In [6], GB-InSAR was used to monitor the deformation of talus slopes during excavation, and real-time dynamic landslide warning during excavation was achieved by calculating the change rate of the cross-section of the equidistant body of the slope. Landslide interior monitoring also plays a significant role in supporting the development of slope stability models [7; 8]. Study [9] demonstrated the significance of temporal resolution in capturing landslide deformation behavior, and found that the tilt meter and AEWG (acoustic emission monitoring using active waveguides) both captured all phases of the activation motion with sufficient temporal resolution. Study [10] found that the combined approach with the tilt meter and rain gauge can reduce the false alarms issued. The appearance of excessive pore water pressure in the landslide can also be used as an indicator of landslide failure and employed in the early warning of landslides [11; 12; 13]. With rapidly developing technology and growing awareness of the monitoring value, such sensors and technologies are expected to become more widely used in the future. Due to the complexity of landslide occurrence in terms of the geological conditions, genesis mechanism, and external influencing factors, problems related to accurate landslide warnings cannot be solved fundamentally by purely relying on deformation monitoring [14; 15; 16]. Numerical simulation techniques have become an effective means to solve these problems. With the rapid development of mechanical theory and numerical simulation methods, finite difference, finite element, and boundary element methods have been widely applied in landslide applications [17; 18]. Studies [19; 20] adopted FLAC3D software to analyze landslide deformation characteristics and damage mechanisms and analyzed the effect of reservoir water level changes on slope stability. Study [21] analyzed the influence of rainfall and groundwater on slope stability using the finite difference method, and it was found that rainfall is a direct factor affecting the landslide failure, while groundwater has a facilitating effect. The authors of [22] used the finite element method to simulate the deformation process of a landslide and found that rainfall and a rapidly declining water level were the main factors leading to landslide displacement. However, determining physical and mechanical parameters of rock and soil mass is crucial for establishing numerical models. The displacement back-analysis method [23; 24], which uses field monitoring data to modify numerical models, is able to invert reliable equivalent physical and mechanical parameters, and has been successfully applied in engineering practice [25].