A double Seismic Array Experiment on Mt. Etna

INGV - Osservatorio Vesuviano

On September 1999 two seismic antennas (array) and a profile of 3-D stations
equipped with short period seismometers were installed on Mt. Etna; Aims of the experiment
were to investigate the structure and the polarisation parameters of the volcanic tremor
wavefield radiated in eruptive conditions, and to measure the seismic velocities and
attenuation in the shallow structure beneath the arrays. The first array was installed close to
Pizzi Deneri Volcanological Observatory, East of the crater area; the second array was located
close to Torre del Filosofo site, south of the crater area. The profile was set up close to the
Pizzi Deneri array. It had a length of 600 meters and consisted of 16 short period 3-
component stations. In addition, a circular array of 8 short period seismometers was set up
around the main crater area (Fig. 1). Several tremor samples and explosions quakes were
recorded in 10 days of operation .
Spectrograms show predominant energy into 1-4 Hz frequency band. Slowness spectra
indicate a predominant source of the tremor located at surface and coincident with the crater
area. Polarisation analysis show that the direction of predominant motion is transverse with
respect to the direction pointing to the active craters.