Estimation of Coda Wave Attenuation in the North of Sanandaj-Sirjan Zone

In this study, for estimating of coda wave attenuation in the North of Sanandaj-Sirjan Zone the seismograms of earthquakes recorded at the seismic stations which located at the longitude of 48°-50° and latitude of 38°-40° have been used. The data with an epicentral distance less than 200 km and a signal to noise ratio equal to or greater than 3 were used. Due to the volumetric percolation of the coda waves from the medium, the variation in coda waves quality factor was investigated in both lateral and depth, and the results were compared with the values obtained for other regions of Iran and the world. After applying the intermediate filter on waveforms in 10 frequency bands, the quality factor was estimated, and finally, the mean values of the quality factor and frequency dependence factor in the region by using two single-back-scattering and single-isotropic-scattering obtained QC꞊149 ± 9f0.66 ± 0.03 and QC꞊152 ± 12f0.66 ± 0.03 respectively. The comparison of the results with the values have been obtained in Central Iran (Qc꞊94f0.97), Alborz (Qc꞊79f1.07) and Southeast Zagros (Qc꞊72f1.19) indicate more homogeneity in the shallow depth layers and seismicity is lower than Central Iran, Alborz and Zagros. Also, for investigating the depth variations of the quality factor in the region, 11 lapse time window lengths were used in 5 seconds increments. The window lengths are begin from 10 seconds. In the lower window lengths, the low Q0 values represent high heterogeneity in shallow depths of the earth.