Mechanical Stability Of Mt. Vesuvius Volcano: Effects Of Asymmetries On The Stress Field

The effect of nonaxisymmetric elasticheterogeneities on the mechanical stability of a nearly axisymmetricvolcanic structure, with particular reference to Mt. Vesuvius (Italy) is investigated. This is done solving numerical models using a finite element codein the framework of linear elasticity. The models include gravity,anisotropic depth-dependent regional stress, the edifice, thepossible presence of a pressurized feeding system and of heterogeneities inthe elastic behavior of country rocks. The criteria to assessinstability are the development of tensile stresses and, in compression, theNavier–Coulomb criterion. The presence of asymmetric heterogeneous structureswith lateral elastic contrast has been considered by solvingthree-dimensional (3D) models. To have computationally tractable models, axis-symmetric models were solved first, considering lateral symmetricheterogeneities of different shapes and sizes around the symmetry axis. This allowed us to assess the minimum size of smallermodels (submodels) to be developed in 3D. Thesubmodels were then solved including asymmetrical heterogeneities.In all the analyzed cases, the main characteristics of theinstabilities/stabilities found with the 3D asymmetric models are verysimilar to those found by the analogous symmetric models.Moreover, the presence of sharp lateral elastic contrast at shallow depthappear to produce a greater instability on the flanks of the volcanicedifice.