Failure mechanism and kinematics of the Tonghua landslide based on multidisciplinary pre- and post-failure data.

Knowledge of kinematics is crucial for understanding landslide mechanisms and assessing hazards. However, characterizing landslide kinematics is often challenging because landslides are sudden events with spatial and temporal coverage. Combining field investigations and remote sensing, the present study reveals the kinematic features, evolution processes, and triggering mechanism of a translational debris slide (the Tonghua landslide) that occurred on August 8 of 2017 in Sichuan Province, China. Based on digital orthophoto maps and digital elevation models derived from unmanned aerial vehicle photogrammetry, 3 years of post-failure kinematics were surveyed in detail. The landslide body experienced moderate-velocity (1.19–3.98 m/d) to slow-velocity (33.2–205.5 mm/d) sliding, eventually entering a period of very-slow-velocity (0.1–1.0 mm/d) sliding. A long-term pre-failure creeping process in the source area of the landslide was detected by interpreting interferometric synthetic aperture radar data and satellite images. At the front part of the source area, the observed deformation velocity was 15–25 mm/year between November 7, 2014 and July 30, 2017. Additionally, the source area of the landslide was found to be located on a hollow slope within a cirque catchment of ~ 67,500 m2. This complicated topographic feature promoted groundwater infiltration and long-term slope creeping; indeed, the 2008 Wenchuan earthquake may have aggravated surface cracking and soil weakening. Long-term creep of the slope caused cracking, saturation, and deformation of the soil body. Finally, seismic effects caused by tunnel blasting triggered sliding of the deformed soils. [ABSTRACT FROM AUTHOR]