Deformation characteristics and reactivated failure modes of the massive Baimu ancient landslide deposit on the northern margin of the East Himalayan syntaxis

In the Eastern Himalayan syntaxis, massive Quaternary loose deposits represent a typical product of abrupt topographic changes. Influenced by the Qinghai-Tibet Plateau uplift and rapid river incision, the partial or complete failure of these deposits is a recurrent phenomenon in alpine-gorge regions, posing substantial threats to major infrastructure development. Through topographic interpretation and field investigation, this study clarifies the geological features and genetic mechanisms of the Baimu ancient landslide deposit (BALD), located on the northern margin of the East Himalayan syntaxis. The surface deformation time series spanning October 2017 to December 2019 was estimated using employing multitemporal synthetic aperture radar interferometry. Then, the spatiotemporal deformation characteristics of the BALD was analysed by superposing terrain factors, and hazard division was implemented. The results indicate that high-hazard zones are mainly distributed on high and steep free faces of the BALD. Deformation evolution and rainfall time series showed obvious correlation. Lastly, a generalized failure model is established for the BALD, which will serve as a valuable reference for disaster prevention and is applicable to the study of similar deposits in the Qinghai-Tibet Plateau. Through topographic interpretation and field investigation, this study clarifies the geological features and genetic mechanisms of the Baimu ancient landslide deposit (BALD). The spatiotemporal deformation characteristics of the BALD were analysed using SBAS-InSAR, and hazard division was implemented by superposing terrain factors. The deformation evolution of the BALD showed an obvious correlation with rainfall time series. Erosion-type progressive multistage failure emerges as a typical failure mode of the BALD. image