Spatial and temporal evolution of mining-induced sinkholes in the Gavorrano area (Tuscany, Italy): Insights from remote sensing and field data

Abstract

The failure of underground cavities and the formation of sinkholes is a major risk at both active and dismissed mining areas. However, while ground deformation related to most active mines is constantly monitored today, the ground instabilities around historical and dismissed mining areas often remain disregarded. Here, we combined a multidisciplinary dataset of historical mining reports and maps, aerial images, field measurements and InSAR observations to reconstruct the spatial and temporal evolution of ground deformation around a sinkhole prone area in the mining district of Gavorrano (Tuscany, Italy). We identified the three sinkholes of Monte Calvo, Valsecchi, and Ravi, with the latter two never reported in literature. The three sinkholes have a spatial correlation with the underground cavities and galleries of major mines. InSAR observations between 20162022 also revealed that an area of ∼ 700 m × 400 m around the Monte Calvo sinkhole is still subsiding with rates of ∼5 mm/yr. Conversely, no clear evidence of deformation is observed at Valsecchi, Ravi, and the nearby city of Gavorrano. Our observations suggest that the sinkhole activity in Gavorrano has been induced by the mining activity in the area and that subsidence is still ongoing at Monte Calvo.