Shear-wave polarization alignment on the eastern flank of Mt. Etna volcano (Sicily, Italy)

F. Bianco, M. Castellano, G. Milano, G. Vilardo

Abstract


Recently, with the improvement of three-component seismic networks, studies revealing anisotropic characteristics in different regions have assumed great interest. In a complex volcanic area like Mt. Etna (Sicily, Italy), the existence of both iso-oriented fault systems and intrusive bodies consisting of olivine and clinopyroxene suggest the presence of anisotropic structures. In order to investigate this we analyzed the physical phenomenon of shear-wave splitting since under certain constraints, shear waves are less sensitive to local heterogeneity. The aims of this paper are: 1) to evaluate if in a structural complex situation like that at Mt. Etna the signal crossing an anisotropic volume could be enhanced in spite of effects due to undirectional properties along the source-receiver path; 2) to investigate the correlations, if any, between polarization direction of the leading shear wave and the patterns of compressive stress acting on the investigated area. Therefore we measured time-delays between the S-onsets on the horizontal components of 3D seismograms to reveal the possible seismic anisotropy in the Etnean region; moreover, we analyzed the polarization vector of shear-waves seismic data recorded during a survey carried out in the spring-summer 1988. We found clear evidence of splitting that we attributed to the presence of an anisotropic volume not homogeneously distributed on the eastern slope of Mt. Etna volcano.

Keywords


anisotropy;Mt. Etna;polarisation;splitting;S-wave

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References


DOI: https://doi.org/10.4401/ag-3980
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X