Collapse susceptibility map in abandoned mining areas by microgravity survey: A case study in Candado hill (Málaga, southern Spain)

The presence of disused gypsum mine galleries in Candado hill (Málaga, southern Spain) has caused constructions at the western end of the hill to collapse. The mine, which closed in the 1960s, is disconnected from the surface. Therefore, the precise dimensions and position of the galleries are unknown, making it essential to undertake a thorough microgravity study to assess the collapse susceptibility of the area. On the one hand, we analyze the accuracy of the terrain correction and Bouguer anomaly calculation, varying density values. This study shows that higher density values produce more pronounced residual minima corresponding to the mine galleries. On the other hand, the approximate mine gallery positions and dimensions were derived through forward modelling, then correlated with the gravity residual anomalies produced in the hill. Altogether, these results can be presented as a collapse susceptibility map relating the areas containing mine galleries with shallow voids on the hill.