APPROACH TO THE VOLCANIC TREMOR BY COVARIANCE ANALYSIS - APPLICATION TO THE 1989 ERUPTION OF MT-ETNA (SICILY)

Polarization of the tremor wavefield, recorded during three periods of the 1989 eruption of Mt. Etna at a temporary array of three-component stations, is analyzed by use of a polarization filter. The tremor shows steady horizontal, near-linear, west-east polarization at all stations. Such a behaviour, which could be coherent with a P-wavefield radiated by a vertical extended source with overall north-south alignment, excludes confinement of the source to the only active vent and is tentatively linked to activity of the main dyke-system of Mt. Etna.