A double Seismic Array Experiment on Mt. Etna

Abstract

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.