Recent Advances in High Spatial Resolution Geophysical Monitoring of Moisture-Induced Landslides

Time-lapse geophysical methods are increasingly used to monitor unstable slopes prone to hydrological destabilisation. Geophysical methods are well suited to this purpose due to the high spatiotemporal resolutions at which monitoring data can be acquired. In particular, geoelectrical and seismic approaches are shown to be particularly beneficial for identifying variations in landslide systems at high spatial resolutions. The integrated use of these approaches, which are sensitive to closely inter-related hydrogeological features and processes driving moisture-induced slope instabilities, can reveal the evolving properties of subsurface materials as they move toward failure. Here, we highlight recent advances in high spatial resolution geophysical monitoring with examples from the Hollin Hill Landslide Observatory, a slow-moving, clay-rich, moisture–induced landslide located in North Yorkshire, UK. We present the details of different high spatial resolution geophysical monitoring arrays deployed at the site, including electrical resistivity, seismic refraction, self-potential, and passive seismic, and consider their relative benefits and weaknesses. Focusing on electrical resistivity and seismic refraction monitoring data, we demonstrate how the integrated analysis of time-lapse data can be used to better understand the key hydrogeological features and processes leading to slope failure.