In this study 50 seismic events, preceding andaccompanying the eruptions occurring in 1981 and 1983,have been considered. Seismic moments, fault radii, stressdrops and seismic energies have been calculated usingBrune’s model (J Geophys Res 75:4997–5009, 1970; JGeophys Res 76:5002, 1971); site, anelastic attenuationalong the propagation path, geometrical spreading andinteraction with the free surface effects are taken intoaccount. For each event we have also estimated theequivalent Wood–Anderson magnitude (MWAeq) (Scherbaumand Stoll in Bull Seism Soc Am 73:1321–1343,1983); relations among all these source parameters havebeen determined. Furthermore, the hypothesis of self-similarity(Aki in J Geophys Res 72:1217–1231, 1967) is notverified for events with seismic moments \1012 N-m: infact the relationship between log-stress drop and logmomentis linear up to a moment of 1012 N-m (events of1981 eruption), while for higher moments (events of 1983eruption) the slope of the regression line is not significantlydifferent from zero. We suppose that such a behaviour isrelated to a heterogeneous medium with barriers on thefaults. Finally, the main conclusion is that eruptions of1981 and 1983 differ from one another both in eruptive andseismic aspects; analysis of seismic energies indicates anincrease in Mt. Etna’s activity, confirmed by studies performedon the following lateral eruption of 1991–1993(Patane` et al. in Bull Volcanol 47:941–952, 1995), occurringon the same structural trend.
Focal parameters of seismic sources during the 1981 and 1983 eruption at Mt. Etna volcano (Sicily, Italy)
IMPOSA, Sebastiano
2008-01-01
Abstract
In this study 50 seismic events, preceding andaccompanying the eruptions occurring in 1981 and 1983,have been considered. Seismic moments, fault radii, stressdrops and seismic energies have been calculated usingBrune’s model (J Geophys Res 75:4997–5009, 1970; JGeophys Res 76:5002, 1971); site, anelastic attenuationalong the propagation path, geometrical spreading andinteraction with the free surface effects are taken intoaccount. For each event we have also estimated theequivalent Wood–Anderson magnitude (MWAeq) (Scherbaumand Stoll in Bull Seism Soc Am 73:1321–1343,1983); relations among all these source parameters havebeen determined. Furthermore, the hypothesis of self-similarity(Aki in J Geophys Res 72:1217–1231, 1967) is notverified for events with seismic moments \1012 N-m: infact the relationship between log-stress drop and logmomentis linear up to a moment of 1012 N-m (events of1981 eruption), while for higher moments (events of 1983eruption) the slope of the regression line is not significantlydifferent from zero. We suppose that such a behaviour isrelated to a heterogeneous medium with barriers on thefaults. Finally, the main conclusion is that eruptions of1981 and 1983 differ from one another both in eruptive andseismic aspects; analysis of seismic energies indicates anincrease in Mt. Etna’s activity, confirmed by studies performedon the following lateral eruption of 1991–1993(Patane` et al. in Bull Volcanol 47:941–952, 1995), occurringon the same structural trend.File | Dimensione | Formato | |
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