Finite element modelling of topographic effects on elastic ground deformation at Mt. Etna

Topographic effects on elastic ground deformation at Mt. Etna have been simulated by a finite element approach. A large grid of isotropic sources of pressure, spaced at 0.5 km in the three dimensions, has been simulated in a given volume, from the volcano's summit to 10 km below sea level (b.s.l.). Theoretical ground displacements computed by the finite element method, incorporating the real topography of the volcano, have been compared to analytical results computed for a half-space. The difference between the displacement obtained from the two hypotheses describes the effect of volcano topography on ground deformation at Mt. Etna. In addition, this study provides insight in the approximated methods which can be used to correct at the first order for topographic effects the results from simple analytical methods in half-spaces. The results of this study also suggest the use of tabulated corrections to add the FEM topographic effect to half-space models. This approach gives the first picture of fully 3D topographic effects at Mt. Etna, which can be used to carefully interpret observed ground deformations and in particular SAR derived images.