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 Bam 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 (Qc) has been estimated using the single back-scattering model. The quality factors Qp, Qd (P and direct S-waves) have been estimated using the extended-coda normalization method. Qi and Qs (the intrinsic and scattering attenuation parameters) have been estimated for the region. The values of Qp, Qd, Qc, Qi and Qs show a dependence on frequency in the range of 1.5–24 Hz for the Bam region. The average frequency-dependent relationships estimated for the region are Qp=(36±6)f(1.03±0.06), Qd=(59±8)f(1.00±0.03), Qc=(79±5)f(1.01±0.04), Qs=(131±4)f(1.01±0.04) and Qi=(104±6)f(1.01±0.05). A comparison between Qi and Qs 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 Qo values at different stations suggest a low value of Q indicating a heterogeneous and attenuative crust beneath the entire region.

► We estimated the attenuation properties, Qp, Qd, Qc, Qi and Qs, in the Bam region, East-Central Iran.
► The variation of Q with frequency and lapse time shows that the lithosphere becomes more homogeneous with depth.
► The estimated Qo values at different stations suggest a low value of Q indicating a heterogeneous and attenuative crust beneath the entire region.
► A comparison between Qi and Qs shows that intrinsic absorption is predominant over scattering.