Estimation of coda wave attenuation in East Central Iran

The attenuation of coda waves, Q(c), has been estimated in Zarand, Jiroft, and Bam regions of east central Iran using a single back-scattering model of S-coda envelopes. For this purpose, the recordings of 97 earthquakes by three seismic networks and a local strong ground motion network have been used. In this research, the frequency-dependent Q(c) values are estimated at central frequencies of 1.5, 3, 6, 8, 12, 16, and 24 Hz using different lapse time windows from 20 to 60 s. The frequency-dependent relationships obtained are Q(c) = (102 +/- 8) f((0.89 +/- 0.05)) for Zarand, Q(c) = (113 +/- 6) f((0.91 +/- 0.06)) for Jiroft, and Q(c) = (79 +/- 5) f((1.01 +/- 0.04)) for Bam region. From the strong ground motion data, we obtain the relation Q(c) = (104 +/- 8) f((0.90 +/- 0.1)). The Q(c) frequency-dependent relationship for the entire region of east central Iran from all data (both seismograms and accelerograms) is Q(c) = (101 +/- 6) f((0.94 +/- 0.11)). The average Q(c) values estimated and their frequency dependent relationships correlate well with a highly heterogeneous and highly tectonically active region. Results also show that the attenuation is higher in Bam region compared to Zarand and Jiroft regions.