Hazard Assessment of Earthquake-Induced Landslides Based on a Mechanical Slope Unit Extraction Method, A Case in Ghana

Abstract. Slope unit extraction is integral to earthquake-induced landslide analysis. The conventional watershed and hydrological slope unit extraction methods are precarious with a sudden change in slope gradient along the flow direction, which result in slope unit heterogeneity, conjoint slopes, and boundary defects of the extracted slope unit. This paper addresses this research gap by proposing a mechanical slope unit extraction method that combines watershed points, hydrological, and segmentation methods. This proposed method defines a slope unit as a closed homogeneous space of points overlaid by a mesh having a variance in the slope gradient along its flow direction. The method extracts and uses 3D points to solve slope heterogeneity defects associated with the conventional watershed methods, segmentation to solve boundary defects, and considers the slope pattern and incident ray at a depth to estimate the possibility of earthquake-induced landslides. Ghana (West Africa) is selected to test the proposed slope unit extraction method. The result shows that the method overcame boundary problems, heterogeneity, sudden gradient change, and conjoint slope unit defects associated with the conventional watershed and hydrological method and shows a uniform slope unit for landslide analysis in Ghana. The landslide prediction rate of Ghana also presents 70.9 % landslide inventory, giving an estimated threshold displacement of 9 cm.