[S03-2] Imaging of heterogeneities in the Earth with seismic scattered waves and ambient noise II

[S03-2-01] Intrinsic and Scattering Seismic Attenuation in Eastern Iran

^○Majid Mahood (International Institute of Earthquake Engineering and Seismology (IIEES),Tehran, Iran)

The attenuation properties of the crust in the Eastern Iran have been investigated. For this purpose, 198 local and shallow earthquake waveforms recorded on a broad-band seismic network, have been analyzed to compute the variation of intrinsic and scattering attenuation parameters with depth from coda waves. We have estimated the quality factors of coda waves (Qc), P and S-waves (Qp, Qs) using the single backscattering model and the extended-coda normalization method, respectively. Qi and Qsc (the intrinsic and scattering attenuation parameters) have been estimated for the region. The average frequency-dependent relationships estimated for the region are Qp=(40±5)f (0.99±0.04), Qs=(54±6)f (1.02±0.03), Qc = (97±5) f (0.94±0.04), Qsc = (149±4) f (1.17±0.04) and Qi = (84±6) f (0.96±0.05). A comparison between Qi and Qsc shows that intrinsic absorption is predominant over scattering. As Q values for larger lapse time windows are affected by heterogeneities variation with depth, this indicates that with increasing depth relative effect of intrinsic attenuation with respect to that of scattering attenuation on coda attenuation decreases in the area under study. Qc values are close to Qi, indicating that coda Q can be a reasonable estimate of intrinsic Q.