Static stress changes induced by the magmatic intrusions during the 2002–2003 Etna eruption

The shallow intrusive processes that occurred during 2002–2003 Etna eruption, as
well as the complex interaction between the magma intrusive events and the tectonic
response of the volcano’s eastern flank, are investigated with numerical deformation
modeling and the estimation of changes in the static Coulomb stress. Ground
deformation and volcanologic evidence clearly indicate a composite mechanism of
intrusion on both the southern and northeastern flanks of the volcano. Geodetic data
inversions have been based on a homogeneous elastic half-space model, although
geological data and seismic tomography indicate that Mt. Etna is elastically
inhomogeneous and that rigidity layering and heterogeneities are likely to affect the
magnitude and pattern of the deformation field. To account for topographic effects, as well
as a complicated distribution of material properties, we use the finite element method
(FEM) to provide a more realistic model. The presence of medium heterogeneity
strongly affects the amplitudes of the static stress changes. Seismicity matches well
the areas of positive increase in the static stress caused by the intrusive events along the
southern and northeastern flanks. The changes in the state of stress generated by the
southern dike produce an extensional stress field that favors magma propagation along
the north-east Rift. The highest seismic releases were associated with the activation of
two fault systems, the Timpe Fault System and the Pernicana Fault. The static stress
changes resolved onto these faults indicate that the magma intrusions on the southern
and northeastern flanks encouraged these seismogenic structures to slip.