Seismological Aspect of ۲۶ December ۲۰۰۳ Bam Earthquake

A waveform inversion algorithm, based on least square method, has been applied to the P and S waves of the ۲۶ December ۲۰۰۳ Bam earthquake. The aftershocks of this event distributed along a narrow zone (approximately ۲۰km) in N-S direction. In this research, estimates of centroid depth, seismic moment, and source mechanism have been obtained. The source mechanism derived from the inversion of long period body waves revealed that two events occurred on N-S trending strike-slip fault with a thrust component. According to the source model estimated in this study, the Bam earthquake was a multiple event. The rupture following the first event started at a depth of about ۸km. However depth of the second event is about ۱۰km. The total seismic moment estimated from inversion processes is ۸.۳۴×۱۰۱۸Nm. The seismic moment of the second event is less than the first one (the seismic moment of second event is calculated as ۲.۳۴×۱۰۱۷Nm). The pulse duration of main shock and the second event was determined from source time function and it is ۱.۷s and ۰.۸s respectively. Corner frequency and source radius have been calculated for main shock and the second event by using pulse duration. The range of corner frequency and source radius are from ۰.۱۸۷Hz -۰.۳۹۷Hz and ۵.۴۷km-۲.۵۷km for main shock and second event, respectively.