Joint application of Ground-penetrating Radar and Electrical Resistivity Tomography for collapse risk assessment in the Madrona sinkhole (Segovia)

Carbonate rocks are frequently affected by dissolution from rainfall and groundwater. As dissolution progress, the roof of the cavities can rapidly collapse originating landforms named sinkholes. When this kind of structures affect to human activities, they constitute a serious natural hazard. The province of Segovia has abundant examples of karst features developed on carbonate rocks. The ‘Sima de Madrona’, a collapse sinkhole located near the city of Segovia, constitutes one of these examples. The aim of this work is to determine the presence of galleries and cavities around this karst feature by means of shallow geophysical techniques, in order to assess the collapse risk of the area. The joint use of Ground-penetrating Radar and Electrical Resistivity Tomography has allowed determining the presence of two cavities related to the sinkhole development. The detection of these small galleries can affect the anthropogenic activities of the area and so, it constitutes a natural risk that has to be taken into account in order to minimize the damages that the collapse of these structures could produc