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.