VELOCITY AND SPECTRAL CHARACTERISTICS OF THE VOLCANIC TREMOR AT ETNA DEDUCED BY A SMALL SEISMOMETER ARRAY

A small L-shaped short-period seismic array was set up at Etna Volcano to measure the wave velocity and the incoming azimuth of the volcanic tremor generated by the volcanic activity at Etna in non eruptive-con ditions. Cross-correlation techniques were used to measure the phase-s hifts between the array stations. An approximately N-S direction of th e progaption direction was estimated, coincident with the azimuth of t he crater area of Etna. An apparent velocity of less than 500 m/s was estimated, suggesting a surface propagation of the tremor waves. Spect ral analysis, confirming previous results, shows velocity spectra peak ed at approximately 2 Hz. A localized source, coincident with the crat er area, agrees with our data and could generate the volcanic tremor a t Etna in non-eruptive stages.