Seismic response to volcanic processes at Mount Etna: coupling thermomechanical simulations with seismic wave-equation modelling

Mt. Etna, located in the north-eastern area of Sicily (Italy), is one of the most active and hazardous strato-volcano in the world, both in terms of paroxysmal events and continuous effusive activity from the summit area and hazardous flank eruptions. Long-term processes of deep magma recharge and storage within the upper crust, passive magma ascent along pre-existing weaknesses, and forceful dyke intrusions allow magma to rise to the surface. Past studies provided evidence supporting the view that the interplay between magma dynamics and storage and the thermomechanical response of the host medium control magma rise and the brittle seismic response of the volcano basement and edifice.

To investigate this interplay, we created a 3D thermomechanical geodynamic model of Etna and the ground deformation response to different geological processes such as magma intrusion, gravitational spreading and main fault systems, especially with regard to the sliding of the southeastern flank. We used the Lithosphere and Mantle Evolution Model (LaMEM) code and achieved a higher model resolution by containerizing the code on the Open Computing Cluster for Advanced data Manipulation (OCCAM), an HPC cluster operated by the University of Turin and the Sezione di Torino of the Istituto Nazionale di Fisica Nucleare.

The model domain covers 41 x 39 x 14km in x, y and z direction and has two greater crustal layers with a horizontal boundary at z = 3.6km, which are inferred from laboratory results, with real topography implementation. The geometry of the flank and the position of the northern and southern fault boundary layers are based on geological evidences. Below the flank is a similar geometry that should function as a weakzone and control the sliding of the flank. Geometry and position of the high-velocity and fluid/gas pockets are based on Vp and Vp/Vs. The position of the two magma storages are inferred from geodetic outcomes. As LaMEM framework allows retrieving both deformation and gravity responses to the final model, we are currently achieving model results that ideally fit the actual GPS data recorded over 20 years in order to determine the rheological laws driving the long-term deformation.