Variation of intrinsic and scattering attenuation of seismic waves with depth in the Bam region, East-Central Iran

The attenuation properties of the lithosphere in the Barn region, East-Central Iran, have been investigated. For this purpose, 42 local earthquakes having focal depths less than 25 km have been used. The quality factor of coda waves (Q(c)) has been estimated using the single back-scattering model. The quality factors Q(p), Q(d) (P and direct S-waves) have been estimated using the extended-coda normalization method. Q(j) and Q(s) (the intrinsic and scattering attenuation parameters) have been estimated for the region. The values of Q(p) Q(d), Q(c), Q(j) and Q(s) show a dependence on frequency in the range of 1.5-24 Hz for the Barn region. The average frequency-dependent relationships estimated for the region are Q(p)=(36 +/- 6)f((1.03 +/- 0.06)), Qd=(59 +/- 8)f((1.00 +/- 0.03)), Q(c)=(79 +/- 5)f((1.01 +/- 0.04)), Q(s)=(131 +/- 4)f((1.01 +/- 0.04)) and Q(j)=(104 +/- 6)f((1.01 +/- 0.05)). A comparison between Q(j) and Q(s) shows that intrinsic absorption is predominant over scattering. The variation of Q has also been estimated at different lapse times to observe heterogeneities variation with depth. The variation of Q with frequency and lapse time shows that the lithosphere becomes more homogeneous with depth. The estimated Q(o) values at different stations suggest a low value of Q indicating a heterogeneous and attenuative crust beneath the entire region. (C) 2011 Elsevier Ltd. All rights reserved.