Seismic codaQand scaling law of the source spectra at the Aeolian Islands, southern Italy

Abstract

The model developed by Aki and Chouet for the coda wave generation and propagation has been used to calculate the quality factor Q for the zone of the Aeolian Islands, southern Italy, in the frequency range of 1 to 12 Hz, and the scaling properties of the seismic spectrum in the magnitude range of 0.4 to 4.7. The Q found for the Aeolian area has a frequency dependence of the form Q = qfv. The absolute values of Q seem to be dependent on the station and location of the seismic events, confirming the strong lateral heterogeneities in the geological structure beneath the Aeolian Arc. A temporal variation has been noted in the Q calculated at Vulcano station (VPL) in a period of 3 weeks soon after the occurrence of a main shock of ML = 5.5 located near the station. The scaling behavior of this sequence is similar to that obtained in two areas of California and one portion of Japan, with a corner frequency that remains constant with an increasing seismic moment between magnitudes 1 and 4. It differs substantially from the scaling properties of the Hawaian earthquakes that show a linear pattern, without an increase of the stress drop with magnitude. The fact that Vulcano is an active volcano seems not to influence the scaling properties of the seismic sequence localized very near it. It probably indicates that the aftershocks used for calculating the scaling law are generated out of the volcanic complex Lipari-Vulcano, in a zone with a good capability of accumulating the stress.

Small-Scale Volcanic Structures of the Aeolian Volcanic Arc Revealed by Seismic Attenuation

“…The velocity structure of the region has been considered in a number of studies (e.g., Chiarabba et al, 2008;Díaz-Moreno et al, 2018), including those with a focus on Stromboli (e.g., Chouet et al, 1998;Petrosino et al, 1999;La Rocca et al, 2000;Petrosino et al, 2002;Linde et al, 2014). Recently, Del Pezzo et al (2019) obtained an average value of intrinsic and scattering attenuation, giving the first approximation of the average attenuation behaviour of the region since the work of Del Pezzo et al (1983). These results show that on average this region has much stronger scattering attenuation behaviour than that around Mt.…”