Three-dimensional geophysical anatomy of an active landslide in Lias Group

8 A geoelectrical investigation of a slow moving earth slide-earth flow in Lower Jurassic Lias Group 9 rocks of the Cleveland basin, UK, is described. These mudrock slopes are particularly prone to failure 10 and are a major source of lowland landslides in the UK, but few attempts have been made to 11 spatially or volumetrically characterise the subsurface form of these slides. The primary aim of this 12 study was to consider the efficacy of fully three-dimensional geoelectrical imaging for landslide 13 investigation with reference to a geological setting typical of Lias Group escarpments. The approach 14 described here included a reconnaissance survey phase using two-dimensional electrical resistivity 15 tomography (ERT), resistivity mapping, self-potential (SP) profiling and mapping, followed by a 16 detailed investigation of an area of the landslide using three-dimensional (3D) ERT and self-potential 17 tomography (SPT). Interpretation of the geophysical data sets was supported by surface 18 observations (aerial LiDAR and differential GPS geomorphological surveys) and intrusive 19 investigations (boreholes and auger holes). The initial phase of the study revealed the existence of a 20 strong SP signature at the site consistent with a streaming potential source and established the 21 relationships between the main geological units, the geomorphologic expression of the landslide, 22 and the resistivity of the materials in and around the study area. The 3D SPT model generated during 23 the second phase of the study indicated drainage patterns across the landslide and preferential flow 24 from the low permeability mud rocks into the underlying more permeable sandstone formation. 25 Manuscript Click here to view linked References