Intrinsic and Scattering Attenuations in the Crust of the Racha Region, Georgia

Three hundred and thirty-five local earthquakes were processed and the attenuation properties of the crust in the Racha region were investigated using the records of seven seismic stations. We have estimated the quality factors of coda waves (Q(c)) and the direct S waves (Q(s)) by the single back scattering model and the coda normalization methods, respectively. The Wennerberg's method has been used to estimate relative contribution of intrinsic (Q(i)) and scattering (Q(sc)) attenuations in the total attenuation. We have found that Q(c), Q(s), Q(i) and Q(sc), parameters are frequency-dependent in the frequency range of 1.5-24 Hz. Q(c) values increase both with respect to lapse time window from 20 s to 60 s and frequency. Q(c) and Q(i) parameters are nearly similar for all frequency bands, but are smaller than Q(sc). The obtained results show that the intrinsic attenuation has more significant effect than scattering attenuation in the total attenuation. The increase of Q(c) with lapse time shows that the lithosphere becomes more homogeneous with depth.