Focal parameters of seismic sources during the 1981 and 1983 eruption at Mt. Etna volcano (Sicily,Italy) |
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| Authors: | Sebastiano Imposa |
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| Institution: | (1) Dipartimento di Scienze Geologiche, Università di Catania, C.so Italia, 57, 95129 Catania, Italy |
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| Abstract: | In this study 50 seismic events, preceding and accompanying the eruptions occurring in 1981 and 1983, have been considered.
Seismic moments, fault radii, stress drops and seismic energies have been calculated using Brune’s model (J Geophys Res 75:4997–5009,
1970; J Geophys Res 76:5002, 1971); site, anelastic attenuation along the propagation path, geometrical spreading and interaction with the free surface effects
are taken into account. For each event we have also estimated the equivalent Wood–Anderson magnitude (MWAeq) (Scherbaum and
Stoll in Bull Seism Soc Am 73:1321–1343, 1983); relations among all these source parameters have been determined. Furthermore, the hypothesis of self-similarity (Aki in
J Geophys Res 72:1217–1231, 1967) is not verified for events with seismic moments <1012 N-m: in fact the relationship between log-stress drop and log-moment is linear up to a moment of 1012 N-m (events of 1981 eruption), while for higher moments (events of 1983 eruption) the slope of the regression line is not
significantly different from zero. We suppose that such a behaviour is related to a heterogeneous medium with barriers on
the faults. Finally, the main conclusion is that eruptions of 1981 and 1983 differ from one another both in eruptive and seismic
aspects; analysis of seismic energies indicates an increase in Mt. Etna’s activity, confirmed by studies performed on the
following lateral eruption of 1991–1993 (Patanè et al. in Bull Volcanol 47:941–952, 1995), occurring on the same structural trend. |
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| Keywords: | Mount Etna Magmatic activity Eruptions Seismicity Chemism |
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