High-altitude deformation and reactivation mechanism of large ancient landslides along the Shadingmai section of the upper Jinsha River, Tibetan Plateau

The high-altitude creeping-deformation of large ancient landslides represents a distinctive pattern resulting from the intricate geomorphological and geological evolution along the eastern Tibetan Plateau. The deformation initiates a cascade of hazardous events, including sliding, river blockage, and dam failure. Studying the high-altitude deformation mechanisms of ancient landslides in alpine canyon areas presents formidable challenges. This study narrows its focus to the Shadingmai section in the upper Jinsha River, employing remote sensing interpretation, field investigations, InSAR deformation monitoring, and statistical analysis of regional rainfall data. The development, distribution, and deformation characteristics of high-altitude landslides were investigated. The findings reveal that 30 typical landslides within the study area, which are influenced by regional stratigraphic rock mass structures and lithological characteristics. Notably, InSAR deformation monitoring records a maximum deformation rate of -30 mm/a in the landslides, predominantly exhibiting characteristics of high-altitude deformation. The Shadingmai ancient landslide epitomizes a typical high-altitude landslide, with surface deformations predominantly characterized by tensile cracks, fissures in buildings, scraps, and localized sliding. Drawing upon SBAS-InSAR technology monitoring and regional rainfall data analysis, the result discerns the hysteresis effect and the “step-like” growth pattern in the cumulative deformation of the Shadingmai ancient landslide. In deeply incised canyon areas, large ancient landslides with high-position thrust-type deformation are complex and highly prone to triggering a disaster chain under heavy rainfall, involving high-position shear failure, landslide damming of rivers, and subsequent dam-break flooding. Ultimately, the results of this study furnish a fundamental theoretical basis crucial for preemptive measures aimed at averting large-scale geological disasters in the upper Jinsha River.