Geophysical study of a large landslide affecting the urban area of Albuñuelas (S Spain)

The urban area of Albuñuelas, a small town located to the south of Granada (S Spain), has been developed in terrain affected by a large-scale rotational landslide with very slow rate of movement. Despite this situation, the internal structure of the landslide and how it has evolved to its present state has not been analyzed in depth up to now. In this paper, we present the first study performed on this landslide to define its configuration and characteristics. For this purpose, ambient noise single-station and array measurements were carried out along several cross-sections of the landslide. The inversion of the measurements has allowed for the estimation of the soil stratigraphy at each site of measurement. These geophysical results have been constrained by data from a borehole drilled in the zone and from field observations of the local geology, allowing for the reduction in uncertainties in the results. A geological–geophysical model of the landslide has been built from these data, showing that the landslide thicknesses is greater than 50 m in its central parts and above 60 m in the upper ones. This model reveals that the evolution of the landslide was complex, with several dislodged elements (blocks) that moved in sequence (retrogression) and were partially eroded in order to explain present morphology. The future evolution of this landslide will be controlled by the composition of the materials surveyed along the foot of the valley, being the western part where there are more erodible materials according to the obtained results.