Multi-Method Geophysical Assessment of a Shallow Complex Landslide

Abstract

This study demonstrates the value of combining multiple non-invasive geophysical methods through a case study at a landslide along Highway 7 near Jasper, Arkansas, USA. Geophysical testing was conducted using Multichannel Analysis of Surface Waves (MASW), Horizontal to Vertical Spectral Ratio (HVSR), and Electrical Resistivity Tomography (ERT) along with select borings. Geophysical testing was aimed to provide a high-resolution and almost continuous image of subsurface conditions (including bedrock depth) for the slide area and to locate the groundwater table/highly saturated zones within the slide area which contribute to the slope movement. MASW revealed a highly variable depth to the weathered bedrock along the observed zone of displacement becoming shallower downslope. ERT 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, using a grid pattern HVSR approach, a high-resolution image of the shallow and complex bedrock topography was generated across the slide area providing valuable information for the repair design. Overall, the results of the combined geophysical approach provide a high-resolution image of landslide subsurface conditions which is critical for stability analyses and slope repair design. This integrated geophysical approach offers a more sustainable, rapid, and cost-effective solution for comprehensive landslide characterization and slope stability assessment when combined with conventional methods.

Full Paper