Moment magnitude estimation using Iran strong motion data

In this study, seismic moment, moment magnitude, and the corner frequency of Iranian earthquakes were estimated using the Iran Strong Motion Network (ISMN) data. To estimate the source parameters, Andrews (1986) method in frequency domain is employed. In this study, two horizontal components of the recordings were processed, filtered, and corrected for geometrical spreading and intrinsic attenuation and then have been used in source spectrum calculation. Here, two time windows were selected (1: S-wave and 2: from P- to end of S- window) and the results show that both windows provide acceptable results with similar mean residuals and standard deviations. However, the smallest standard deviation is related to S-window. In total, the moment magnitude for about 4171 records have been calculated. We validated our results for 209 earthquakes with at least three recorded accelerograms that had available reported moment magnitude. The results indicated that the estimated magnitudes are in good accordance with the reported moment magnitudes with mean residual of about 0.07 and standard deviation of about 0.2. This method can be employed in real time or near real time procedure, where both seismic moment and moment magnitude can be calculated soon after the earthquake originated just using available strong motion data. This information would be very helpful in crisis management so that more effective emergency response and recovery plan can be provided in future earthquakes.