Two-dimensional deformation monitoring for spatiotemporal evolution and failure mode of Lashagou landslide group, Northwest China

The Lashagou landslide group in Gansu Province, China, is a typical shallow loess landslide group caused by artificial slope cutting. In April 2018, local sliding of the landslide group damaged houses and blocked the G310 highway, leading to the relocation of the Lashagou village, which aroused widespread concern. Unfortunately, the spatiotemporal displacement characteristics and failure modes of the landslide remain unknown. In this study, a method for the estimation of two-dimensional deformation of landslides, based on the local parallel flow model, was presented. This method only needs two orbital synthetic aperture radar (SAR) images with different imaging geometries, and has high accuracy verified by global satellite navigation system (GNSS) observations. In practice, we first obtained the surface velocity and time series deformation of the ascending and descending orbits. The best-fit sliding direction and inclination of the landslide movement were then inverted by combining satellite imaging geometry and surface velocity. Furthermore, the two-dimensional deformation of the Lashagou landslide group in the sliding and normal directions was obtained. We found that the landslide was in the accelerated deformation stage during the wet season and the deformation was mainly concentrated in the northern part of the Lashagou village. The snowmelt and continuous rainfall were the main factors in the landslide deformation. In addition, the landslide surface displacement characteristics and deep stress states can be linked using a combination of two-dimensional deformation, combined deformation, and inclination, which provides evidence that landslide movement is controlled by one or more deep continuous structural planes. Our research shows that the two-dimensional deformation retrieval method can be applied to gravity-driven translational landslides to help prevent and mitigate landslide hazards.