Echo-resonance and hydraulic perturbations in magma cavities : application to the volcanic tremor of Etna (Italy) in relation to its eruptive activity

摘要: A study is presented of spectral features volcanic tremor recorded at Mount Etna (Sicily, Italy) following the methods analysis suggested by resonant scattering formalism Gaunaurd and Uberall (1978, 1979a, 1979b) model for hydraulic origin Seidl et al. (1981). The periods investigated include summit flank eruptions that occurred between 1984 1993. Recordings from a permanent station located near top volcano were used, temporal patterns associated with (a) average spacing (\(\bar \Delta \)) consecutive peaks in frequency range 1–6 Hz, (b) shape (c) overall amplitude analyzed. \(\bar \) values are thought to depend on physical properties magma, such as its density, which, turn, controlled degree gas exsolution. Variations tentatively attributed changes geometrical boundary conduits magma batches. Finally, should essentially reflect state turbulence within superficial ascending path. limit application given fact fundamental modes integer harmonics difficult identify spectra, sources likely cavities very complex geometry, rather than spherical or cylindrical chambers, expected theory. This gives evidence some correlations analyzed major events activity, related both lava flow explosions vents. In particular, relatively high have been attained during SE crater eruption 1984, eruptive phases September–October 1989 1991–1993 eruption, suggesting presence dense all these events. Conversely, low coincidence December 1985 activity paroxysmal craters early 1990, which interpreted here fed fluid-vesiculated magma. Appreciable modifications observed relation probably preceded opening disactivation shallow dykes seems be sensitive indicator conduits, intense activity.