Estimation of coda wave attenuation in East Central Iran

Abstract

The attenuation of coda waves, Qc, 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 Qc 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 \(Q_c =\left( {102\pm 8} \right)f^{\left( {0.89\pm 0.05} \right)}\) for Zarand, \(Q_c =\left( {113\pm 6} \right)f^{\left( {0.91\pm 0.06} \right)}\) for Jiroft, and \(Q_c =\left( {79\pm 5} \right)f^{\left( {1.01\pm 0.04} \right)}\) for Bam region. From the strong ground motion data, we obtain the relation \(Q_c =\left( {{104}\pm {8}} \right)f^{\left( {{0.90}\pm {0.1}} \right)}\). The Qc frequency-dependent relationship for the entire region of east central Iran from all data (both seismograms and accelerograms) is \(Q_c =\left( {{101}\pm {6}} \right)f^{\left( {{0.94}\pm {0.11}} \right)}\). The average Qc 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.