Characterization of pre- and post-failure displacements of the Huangnibazi landslide in Li County with multi-source satellite observations

Abstract

The Huangnibazi landslide in Li County of southwest China, began to slide rapidly since 8 August 2017. It received little attention before the failure event. The fast motion of the slope posed great threats to the safety of nearby villages and the national highway G317 at the foot of the mountain. In this study, Synthetic Aperture Radar (SAR) datasets collected by C-band Sentinel-1 and X-band TerraSAR-X (TSX), as well as optical images acquired by Sentinel-2 Multi-Spectral Instrument (MSI) over the landslide site were analyzed to characterize the evolution of the slope before and after the failure event. Firstly, the surface change of the sliding area was qualitatively evaluated using the Sentinel-2 true-color images and pseudo-colored TerraSAR-X amplitude images. Next, the slow movement of the slope before the failure event was detected by interferometry using both TerraSAR-X and Sentinel-1 data stacks. The maximum displacement rate estimated was larger than −45 mm/year along the radar line of sight (LOS) direction. Finally, the large post-failure displacements of the landslide were successfully retrieved with meter-level accuracy from TerraSAR-X observations using adaptive amplitude offset tracking method. The maximum displacement decreased from about 30 m in 11 days in August 2017 to 1–2 m in 22 days in January 2018 in both LOS and azimuth directions. According to the recent measurements of surface displacement, the landslide body is becoming stabilized gradually, which suggests that the risk of catastrophic collapse of the slope has been largely reduced.