Site amplification in the Khorasan Seismic Network, Iran, was estimated using small earthquake events (ML 1.6-5.5) recorded from 2003 to 2006. This seismic network consists of 5 broad band stations (NJ, MH, BJ, QU and SB) distributed in Razavi and North Khorasan provinces. A total of 255 three-component waveforms from 88 events were used in this study. The wide dynamic range of the Guralp instrument provided a broadband seismogram for S-waves. Site effects were estimated by linear inversion using the reference site (NJ). The S-wave quality factor was found to be approximated by the relation 165f 0.48 in the frequency range 0.6-10Hz. It was found that the siteamplification factor for three kinds of geometrical spreading model R-1, R-0.75, R-0.5 was similar but the quality factor varied.

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