Separation of intrinsic and scattering attenuation in the crust of central and eastern Alborz region, Iran

In this study, more than 380 local earthquakes (2 < M-L< 4.5) have been used to estimate the direct-shear waves (Q(d)), coda (Q(c)), intrinsic (Q(i)) and scattering quality factor (Q(Sc)) in the crust of central and eastern Alborz region. The events were recorded by one temporary and two permanent networks. The quality factors of shear and coda waves have been individually estimated at different frequency bands by using coda normalization (CNM) method and single backscattering (SBS) method, respectively. Average frequency dependent relationships have been estimated for Q(d) and Q(c) 111 +/- 4f(0.85 +/- 0.04) and 112 +/- 8f(1.02 +/- 0.06), respectively. The intrinsic quality factor, Q(i) has been separated from the scattering quality factor Q(Sc) by using individually estimated Q(c) and Q(d) values. The average frequency-dependent relationships of Q(i) and Q(Sc) have been calculated in the form of 108f(1.00) and 784f(0.56), respectively. The results of this study suggest that S-wave's attenuation (Q(d)(-1)) is dominated by the intrinsic attenuation. The attenuation of coda waves has been observed similar to the intrinsic attenuation, which indicates, the coda decay is mostly caused by the intrinsic attenuation. It has been observed that the scattering mean free path is frequency independent at frequencies greater than 6 Hz. The results of this study are similar to the tectonically active regions. (C) 2016 Elsevier B.V. All rights reserved.