Landslide from the 'inside'

The mapping of internal structures of landslides is a challenging task. However, several investigation methods are commonly used to comprehend the interior of a slope. First, there is direct exploration, such as drilling and trenching, enabling a direct contact to the material of the subsoil. Secondly, there is indirect exploration comprising geophysical techniques, either in boreholes or for surface applications. A most efficient mean to integrate the ensemble of collected subsurface information into a visual format is 3D geo-modelling. It allows the comprehension of multiple 1D and 2D data in a 3D space that can be combined with surface data or imagery of the study area. Here, we present some applications using indirect explorations, i.e. 1D and 2D geophysics (active and passive seismic as well as electric), on landslide slopes in Europe (Mreyen et al., 2017). For the representation of the actual surface of the study area, a high resolution digital elevation model is used, eg. on the basis of LiDAR data. For the subsurface modelling, interpolation techniques are used to link contrasts in physical properties detected in the landslide mass that possibly indicate the vertical and lateral boundaries of the fractured material in contrast to the bedrock (Fig. 1). The latter allows us to define the geometry as well as the volume of the failure and furthermore to better estimate the pre-failure morphology of the studied slope. Such models allow a look in the interior of a landslide, and furthermore encourage the use of virtual reality techniques that can make you ‘dive’ into geology (Havenith et al., 2017).