Extract fine slope units for better seismic landslide susceptibility assessment using twice multi-scale segmentation on DEM grids

Slope unit (SU) extraction is essential for landslide susceptibility assessment. Traditional methods neglect mechanical properties, yielding coarse units with poor stability and uniformity. We propose YaMSS, a novel method integrating topographic and mechanical properties via multi-scale segmentation. It first segments DEM into units with uniform slope aspect, then subdivides them based on yield acceleration (Ya) – a key seismic stability indicator. When applied to Wenchuan County, Sichuan, China, an area heavily impacted by the 2008 Mw 7.9 Wenchuan earthquake, YaMSS generates SUs with high uniformity in both slope aspect and stability, reducing the average size by approximately 97% compared to that with the hydrologic method, and is similar to that with the Huang method. Validation via logistic regression demonstrates that YaMSS captures the spatial heterogeneity of regional landslide susceptibility, achieving the landslide area density in extremely high, and the landslide susceptibility levels of high-position slope was 43.58% for YaMSS – markedly higher than the other two methods. In addition, the permanent displacement analysis verifies that the yield acceleration adopted herein enables rapid seismic landslide hazard assessment under various scenarios. By incorporating mechanical and aspect details, YaMSS offers an enhanced framework for seismic landslide susceptibility assessments in complex earthquake-prone mountain regions.