Structural analysis of fractures, faults and dykes in the Somma-Vesuvio volcano

A geological and structural survey on the Somma-Vesuvio volcanic edifice has been carried out with the main aims to define the contribution of local versus regional stress field in the evolution of the volcano and the relationships between caldera evolution, fractures and faults. Measurements of fractures, faults and dykes were collected, mainly inside the caldera sector, and analyzed to characterize the fracture network affecting volcanic rocks. Structures were recorded both in lavas and pyroclastic rocks. Most of fractures in lavas are cooling joints. Several cooling joint are reactivated as normal faults, following the caldera collapse. Generally fractures both parallel and orthogonal to caldera rim occur. Finally recent fractures are associated to gravity instability of volcano edifice are well evident in the eastern sector of the Mt. Somma. Other normal faults characterized by low angle dips occur along the cliff of Mt. Somma. Dykes appear as planar at places forming an en-echelon pattern or with a ramp-flat geometry. Fractures, dykes and fault show some preferred orientations. A field stress map was carried out from inversion of meso-scale faults and fractures.