5:15 PM - 7:15 PM
[HGM04-P08] Distribution of deep-seated gravitational slope deformation and its controlling factors in the Kii Mountains
Keywords:deep-seated gravitational slope deformation, GIS analysis, Kii mountains
Gravitational slope deformation such as uphill-facing and downhill-facing scarps are found on mountain slopes. Some of these landforms appear before deep-seated landslides. Understanding their distribution and its controlling factors is important for predicting slope hazards and understanding slope processes. In recent years, research has been conducted to clarify the distribution and formation factors of gravitational slope deformation based on field investigations and GIS analysis of high-resolution topographic data. However, further research is needed to examine the controlling factors in a wider range of regions.
This study identified uphill-facing and downhill-facing scarps in the Kii Mountains using an MPI Red Relief Image Map. We then examined relationships between the identified scarps and topographic (elevation, slope angle, relief, stream sinuosity, and the Convergence Index (CI), a proxy for flow convergence and divergence), climatic (annual precipitation), and geologic factors (rock type and geological structures). Uphill-facing scarps were most common at elevations of 800–1000 m, on slopes of 21–30°, near ridges with high CI values, and in areas where the 500 m buffer relief ranged from 300 to 550 m. Downhill-facing scarps were most common at elevations of 650–1000 m, on slopes of 21–30°, near ridges with high CI values, and in areas with 500 m buffer relief ranged from 250 to 550 m. Both types of scarps were more abundant in sedimentary rocks of accretionary complexes than in granite areas. The relationship between gravitational slope deformations and geological structures was examined using strike and dip data from 1:50,000 geological maps. The results showed that deformation was most frequent in underdip cataclinal slopes, followed by overdip cataclinal slopes and anaclinal slopes. A decision tree analysis was conducted to evaluate the relative importance of elevation, slope angle, CI, relief, rock type, precipitation, and geological structure in determining the presence of gravitational slope deformations. The results showed that CI and slope angle more strongly control the distribution of gravitational slope deformations than rock type, precipitation, or geological structures. This finding is consistent with previous studies from other regions. Further investigation is needed to clarify how differences in subsurface structure influence surface landforms. A deeper understanding of these relationships could improve the accuracy of large-scale mapping and analysis of gravitational deformation landforms.
This study identified uphill-facing and downhill-facing scarps in the Kii Mountains using an MPI Red Relief Image Map. We then examined relationships between the identified scarps and topographic (elevation, slope angle, relief, stream sinuosity, and the Convergence Index (CI), a proxy for flow convergence and divergence), climatic (annual precipitation), and geologic factors (rock type and geological structures). Uphill-facing scarps were most common at elevations of 800–1000 m, on slopes of 21–30°, near ridges with high CI values, and in areas where the 500 m buffer relief ranged from 300 to 550 m. Downhill-facing scarps were most common at elevations of 650–1000 m, on slopes of 21–30°, near ridges with high CI values, and in areas with 500 m buffer relief ranged from 250 to 550 m. Both types of scarps were more abundant in sedimentary rocks of accretionary complexes than in granite areas. The relationship between gravitational slope deformations and geological structures was examined using strike and dip data from 1:50,000 geological maps. The results showed that deformation was most frequent in underdip cataclinal slopes, followed by overdip cataclinal slopes and anaclinal slopes. A decision tree analysis was conducted to evaluate the relative importance of elevation, slope angle, CI, relief, rock type, precipitation, and geological structure in determining the presence of gravitational slope deformations. The results showed that CI and slope angle more strongly control the distribution of gravitational slope deformations than rock type, precipitation, or geological structures. This finding is consistent with previous studies from other regions. Further investigation is needed to clarify how differences in subsurface structure influence surface landforms. A deeper understanding of these relationships could improve the accuracy of large-scale mapping and analysis of gravitational deformation landforms.