A Multi-method Geophysical Approach for Complex Shallow Landslide Characterization

This case study demonstrates the value of combining multiple non-invasive geophysical methods to characterize a landslide along Highway 7 near Jasper, Arkansas, USA. Geophysical testing was conducted using Multichannel Analysis of Surface Waves (MASW), Horizontal to VerticalSpectral Ratio (HVSR), and Electrical Resistivity Tomography (ERT), supplemented by select soil borings. The geophysical investigation aimed to provide a high-resolution, near-continuous view of subsurface conditions, including bedrock depth and the location of the groundwater table or highly saturated zones within the slide area. These factors are important contributors to slope instability. The MASW results revealed a highly variable depth to weathered bedrock along the observed displacement zone, with the bedrock becoming shallower downslope. The ERT data detected saturated zones associated with observed seeps and springs in the area, which were feeding water into the unstable zone. A low resistivity zone on the north side correlated to wet spots, while south of the highway, saturation occurred near the deeper bedrock interface. Additionally, a grid-based HVSR approach generated a high-resolution image of the shallow and complex bedrock topography across the slide area, providing valuable information for the slope repair design. Overall, the integrated geophysical approach offered a more sustainable, rapid, and cost-effective solution for comprehensive landslide characterization and slope stability assessment, compared to relying solely on conventional methods. The combined geophysical results provided a detailed, high-resolution understanding of the subsurface conditions influential for stability analyses and slope repair design.