LONG PERIOD IRANIAN STRONG MOTIONS RECORDED DURING1994-2002, PROCESSING AND ANALYSIS

摘要

The recorded strong motion data in Iran since 1994 till the end of 2002 are investigated in order to findthe well recorded (high signal to noise ratio) accelerometric data, specially in the long period ranges. Therecords having low signal to noise ratio in the frequency range of less than 0.3 Hz are excluded, and therest of 100 records are processed and analyzed in this study. The site classification for these records isperformed based on the receiver function method (estimating the H/V ratio for each of the recordedmotions). According to this procedure, the numbers of the selected records were 46, 10, 16 and 28 for thesite classes 1, 2, 3 and 4, respectively. The records are presented based on their code, station name, siteclass, band-pass filter selected for each record, PGA (the greatest of three components), the event's date,epicentral region, moment magnitude, focal depths, focal mechanisms and the hypocentral distances. Thehypocentral distances are estimated for each record based on the s-p arrival time method. 100 recordscorresponding to 15 earthquakes are finally selected. The selected records have different frequencycontents and specifications. This difference corresponds to the magnitude and hypocentral distances, aswell as to the instrument type. Most of the records are noisy in the frequencies less than 0.3 Hz.However, some records show high signal to noise ratios in the frequency band of 0.3Hz or lower. Thefrequency 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 goodquality/recent strong motion records in Iran, having good quality low frequencies contents.