Evolution of large landslides in tectonically active regions - A decade of observations in the Zhouqu County, China

Abstract

The Zhouqu region is located in the middle reaches of the Bailong River in southern Gansu Province. It is recognised as one of the most active geohazards regions in China. This paper presents more than a decade of observations (2010−2023) of the evolution of landslides along an active fault zone in the Zhouqu region. A varied lithology comprises shales and phyllites in a fault-controlled geomorphology that conditions the slopes and has resulted in large ancient landslide complexes. The activity of these landslides was assessed using InSAR (Interferometric Synthetic Aperture Radar), a technique capable of generating historical and recent ground deformation data. These assessments were validated through field investigations. The region hosts 31 active landslides, including four large ancient landslides with areas greater than 1 km², each displaying velocities exceeding 320 mm/year between February 2017 and August 2023. These landslides cover an area of approximately 35.7 km², some 16.4 % of the Zhouqu region (218 km²). The findings suggest that tectonic activity and lithology play critical roles in landslide and landscape development. Gradual changes in climate have the potential substantially alter the precipitation regime, which affects the stability of slopes and the mobility of large, slow-moving landslides. This research highlights the need for long-term monitoring (InSAR plus fieldwork) to achieve a better understanding of the evolution of large landslide in such dynamic regions that are influenced by tectonic, climatic and anthropogenic conditions. This knowledge adds to our understanding of the ways in which humans influence and, in turn, will be influenced by these large slope deformation processes in these dynamic terrains.