# Influence of Earthquakes on Landslide Susceptibility in a Seismic Prone Catchment in Central Asia
## 4 Discussion
### Shortcomings of the Modelling Approach  
This section discusses the main limitations of this study.  
First, this study faced challenges by the lack of adequate input data: (a) the input soil data were calculated based on six representative samples instead of a large number of soil samples; (b) as the grid layer of underground water was not available in this catchment, one averaged pore water pressure value was used for the entire catchment; and (c) the DEM with a resolution of 10 m was used in this simulation, and the generated simulationswith low resolution data may lead to potential inaccuracies (e.g., a lack of representation of the actual on-ground topographic features and an increased loss of detailed properties of LSI and VOL). In this sense, a high resolution of DEM, for instance, the airborne LIDAR (the light detection and ranging, at a resolution of 30 cm or better) data, may support increasing the precision of the simulations, but it will increase the computation time and produce a large size of output files, and this will cause further problems (e.g., longer computation time for further analyses, beyond the limits of the programs, and requirements of advancement in computing facilities which can handle extremely large datasets) for the following statistical analyses.  
Second, the limitations of Scoops3D itself can also affect the simulated results: (a) the limit equilibrium method does not allow progressive failure, and failures can only occur simultaneously along one single failure surface; (b) Scoops3D does not take the site-specific features (e.g., discontinuity of local soil layer, external loads, non-linear strengths, partially submerged slopes, tension cracks, and complex failure-surface geometry) into consideration; and (c) the volume of failure is predefined with the potential slip surfaces. This predefined value can lead to changes in the simulated results and strongly depends on the experiences of the modellers [15].  
Third, from the data preparation to the result generation, uncertainties may be introduced at each stage for the physically-based models. The input variables (i.e., soil parameters and pore pressure) were determined in the laboratory or from scientific experiences. The actual situation of soil and groundwater might be represented with limited accuracy due to a limited number of samples. In addition, the temporal variability of soil materials and pore water pressure caused by long-term erosion, land cover change and climate change (e.g., temperature and precipitation) cannot be considered in the simulations of Scoops3D. Uncertainties regarding the geometric parameters can be introduced by the predefined slip surface. Some simulations assume a shallow-seated landslide, while others assume a deep-seated landslide. Moreover, other site-specific features, as mentioned above, can also contribute to geometric uncertainties [33]. Concerning the earthquake loading, the proposed correlation between the horizontal pseudo-acceleration coefficient and the earthquake magnitude was obtained based on scientific experiences, but was not always in absolute agreement, since the damage of an earthquake can be also affected by many other factors, including the earthquake's depth, its geographical features, and so on. In this sense, follow-up studies should be carried out, particularly when sufficient _in situ_ measurements of the geographical parameters, soil properties, and underground pore water pressure in the Mailuu-Suu catchment have been obtained.  
Last but not least, a calibration between the simulated and measured landslide metrics could not be performed due to the lack of historical earthquake-induced landslide distributions and VOL in this remote area. However, the installation of a turbidity monitoring system is currently being investigated [77], which would allow calibration in the follow-up studies.