Stress interaction between seismic and volcanic activity at Mt Etna

Abstract

International audienceMt Etna lies on the footwall of a large normal fault system, which cuts the eastern coast of Sicily and crosses the volcano eastern flank. These faults are responsible for both large magnitude historical earthquakes and smaller damaging seismic events, closer to the volcano. We investigate here the two-way mechanical coupling between such normal faults and Mt Etna through elastic stress transfer. The comparison between eruptive sequences and historical seismicity reveals that the large earthquakes which struck the eastern Sicily occurred after long periods of activity along the Mt Etna rift zone. The larger the erupted lava volumes, the stronger the earthquake. The smaller earthquakes located on the eastern flank of the volcano occur during periods of rift zone eruptions. We point out that the seismicity rates are well correlated with the rate of erupted lava. By modelling elastic stress changes caused by earthquakes and eruptions in a 3-D elastic half-space, we investigate their interaction. Earthquake dislocations create a vertical stress gradient along fissures oriented perpendicular to the minimum compressive stress and compress shallow reservoirs beneath the volcano. This may perturb the magmatic overpressures in the Etna plumbing system and influence the transport and storage of the magma as well as the style of the eruptions. Conversely, the large rift zone eruptions increase up to several tenths MPa the Coulomb stress along the eastern Sicily normal fault system and may promote earthquakes. We show that the seismic activity of the normal faults that cut the eastern flank of the volcano is likely to be controlled by Coulomb stress perturbations caused by the voiding of shallow reservoirs during flank eruptions

Investigation of Potential Volcanic Risk from Mt. Baekdu by DInSAR Time Series Analysis and Atmospheric Correction

“…Thus, the magma chamber did not significantly contribute to the observed surface deformation during the period of this study. Assuming the absence of major activity in the magma chamber, it was proposed that minor coulomb stress changes of the deep magma chamber induced the clamping and unclamping of fault planes as shown in the case studies by [79,82]. It is characterized by predominantly normal faulting in the focal mechanisms of the 2007 observation towards a tendency of strike-slip faulting in the 2008 observation.…”

“…Since only a few StaMPS/MTI results showed clear surface deformation and produced the source parameters in reasonable ranges, we In the first scenario, a Mogi-type magma chamber of spherical shape in an elastic half-space [70] and four faults lines inferred from [5] were introduced. In this scenario the central magma chamber contributes to surface unrest by volume or pressure changes interacting with the faults lines as shown by, e.g., Feuillet et al [79]. Figure 12 and Table 3 present the observed and modelled Both models were optimized using the Levenberg-Marquardt algorithm (LMA) which was implemented using Gauss-Newton iteration and loops in order to obtain a convergence of the gradient descent [75].…”

Earthquake triggering of mud volcanoes

“…Static stress also plays a significant role in near-field interactions between tectonic earthquakes and volcanic eruptions (e.g. Feuillet et al, 2006;Walter and Amelung, 2006;Walter, 2007;Walter and Amelung, 2007).…”

Unusual magma storage conditions at Mt. Etna (Southern Italy) as evidenced by plagioclase megacryst-bearing lavas: implications for the plumbing system geometry and summit caldera collapse

“…On the basis of the morphometric features of flank cones and their feeding structures, Villari et al (1988) interpreted the development of the eruptive fractures in the medium and upper flanks of the volcano as caused by overpressure of the magmatic column within the central conduit. In this regard, Feulliet et al (2006) also showed that large shallow reservoirs preferentially lead to central or lateral eruptions (connected to the central system) on the medium and upper volcano flanks more than "eccentric" eruptions (flank eruptions not connected to the central system; cf. Rittmann 1973).…”

“…This may prevent the vertical propagation of dykes from depth and promote magma storage in shallow sill-like reservoirs under compression (cf. Feulliet et al 2006).…”