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We analyzed about 150 local earthquakes recorded in Southeastern Sicily from 1994 to 2001 and estimated coda-Q, intrinsic and scattering attenuation. We used the single scattering assumption to fit the amplitude envelopes of the coda at different frequency bands, obtaining a Qc varying with frequency as generally observed in tectonically active areas. Lapse time dependence has been also studied for the area, with the coda waves analyzed at window lengths ranging from 15 to 50 s, provided the coda duration permitted it. We found that Q0 (Qc at 1 Hz) increases with lapse time and we interpreted this as due to increasing Qc with depth. Conversely, the frequency dependence coefficient n is mostly stationary at all the lapse time window lengths.Finally, using the independent estimates of Qc and the total Q (QT) previously obtained for the area by other authors from direct S-waves of the same data set, we separated the intrinsic (Qi-1) from the scattering (Qsc-1) attenuation factor. The results suggest that in Southeastern Sicily intrinsic dissipation plays a predominant role with respect to scattering phenomena. [Copyright &y& Elsevier]

The attenuation of P- and S-waves in Southeastern Sicily was estimated by applying two different methods in time and frequency domains. We analyzed waveforms from about 290 local events (0.6≤ML≤4.6) recorded at a three-component digital network.By applying the pulse broadening method to the first P-wave pulse, we found an average Qp value of ca. 140. The application of the frequency decay method provided a Qp value of ca. 120, in the low-frequency band (3–9 Hz). Conversely, in the high frequency range (16–27 Hz) the average Qp is significantly larger (ca. 640). The frequency decay method was also applied to S-waves spectra. In the low frequency range (2–5 Hz) the estimated average Qs is ca. 190. As for Qp, also Qs, in the high frequency range (16–27 Hz), is larger (ca. 700). These results evidenced a frequency dependence of both the quality factors Qp and Qs, as commonly observed in tectonically active zones characterized by high degree of heterogeneity. [Copyright &y& Elsevier]