Automated quasi-3D reconstruction of landslide slip surfaces using UAV-derived surface displacement

Rapid and safe identification of slip-surface geometry is essential for efficient landslide investigation and mitigation. Conventional approaches to slip-surface determination rely primarily on borehole surveys and in situ instrumentation; however, these methods require long investigation periods and substantial labor.In this study, we propose a new method that automates slip-surface reconstruction using high-density ground-surface displacement vectors derived from multi-temporal topographic data collected by a laser-equipped UAV at two landslides developed in Neogene formations in northeastern Japan. The analysis estimates two-dimensional slip-surface profiles along multiple cross sections (following Ogita et al., 2024), which are subsequently integrated to construct a quasi–three-dimensional slip-surface geometry. For validation, the landslide moving mass volumes estimated using the proposed method were compared with those identified from dense borehole data. The results show agreement rates of 87% and 96%, respectively. These findings demonstrate that the proposed method achieves sufficient accuracy for practical application in future landslide mitigation planning. References：OGITA, S., HAYASHI, K., ABE, S., TSOU, C.-Y. (2024): Estimation of slip surface geometry from vectors of ground surface displacement using airborne laser data : case studies of the Jimba and Tozawa landslides in Akita Prefecture, Journal of the Japan Landslide Society, 61(4) 123-129 （in Japanese with English abstract）.