Formation and distribution of landslides controlled by thrust-strike-slip fault zones and fluvial erosion in the Western Qinling Mountains, China

Abstract

In active orogenic belts, fault zones and fluvial erosion are the two principal factors that control the development of landslides. The Langma-Baiya fault zone (LBFZ) and the Bailongjiang fault zone (BFZ) in the Western Qinling Mountains (WQM) in China are part of an intracontinental orogenic zone, where landslides are the principal geomorphological process. It is also one of the regions with the most severe landslide disasters in China. We established a historical landslide database for the LBFZ and BFZ, based on high-precision remote sensing image interpretation and field investigation. The results indicated a total of 2764 landslides, including 1190 large landslides and 79 giant landslides. The quality of the landslide database was evaluated using the frequency-area curve distribution characteristics, and the results showed that the small-medium size landslides are underrepresented in the database, likely due to the influence of factors such as surface erosion, vegetation coverage, and human activities. Therefore, we focused on the spatial distribution and formation mechanism of large and giant landslides. Landslides are unevenly distributed in space; specifically, our field investigation and statistical analysis of swath profiles revealed that landslides are aggregated within tectonic zones, in areas of weak rock masses, and on the banks of rivers. Finally, based on the combination of the various factors controlling landslides, we divided the study area into three subregions, for which conceptual models were established. These models highlight the importance of the distance of the fault zone to a river, together with the degree of fluvial erosion, in controlling the development of landslides. The combined effects of fluvial erosion, geological structures, and the low-grade metamorphic rocks exposed along fault zones are major controls on the development of large landslides, and the local structural characteristics of thrust-strike-slip fault zones control the type of landslides.