Document Type : Seismology and Engineering Seismology
The recorded strong motion data in Iran since 1994 till the end of 2002 are investigated in order to investigate the well recorded (high signal to noise ratio) accelerometric data, specially in the long period ranges. The records having low signal to noise ratio in the frequency range of less than 0.3 Hz are excluded, and the rest of 100 records are processed and analyzed in this study. The site classification for these records is performed based on the receiver function method (estimating the H/V ratio for each of the recorded motions). According to this procedure, the number of the selected records were 46, 10, 16 and 28 for the site classes 1, 2, 3 and 4 respectively. The frequency contents of most of the records show dominant amplitudes between frequencies 0.2 and 10Hz. The Fmax values are systematically greater for the vertical components comparing to the horizontal ones. This selected catalog of 100 accelerograms obtained from 15 earthquakes provides a basis for the good quality/recent strong motion records in Iran, having good quality low frequencies contents. The response spectra of selected records having a PGA>0.05g are presented in the article and the normalizedmean spectra for the 4 site classes are introduced. The predominant periods of site classes 1, 2, 3 and 4 are found to be 0.09, 0.1, 0.13 and 0.2 sec for horizontal components and 0.08, 0.06, 0.11 and 0.15 sec for vertical components respectively.