| dc.description.abstract | For systemically estimation of the fault parameters and rupture directivity, we developed a new algorithm for the simultaneous determination of the earthquake source parameters, including seismic moment, focal mechanism, rupture length and rupture velocity, using far-field waveforms. The observed waveforms are corrected for instrument response, geometrical spreading and surface effects. The focal mechanism of an earthquake was determined through a grid search, while the pseudo radiation patterns of -wave were obtained for each station. The best solution for the focal mechanism was determined by comparing the pseudo and theoretical radiation patterns for every step on grid search. The source time functions obtained from the stations are, furthermore, to be used to estimate the rupture length and rupture velocity accounted for rupture directivity.
We applied this method to four moderate to large global earthquakes for Mw5.8-7.3. A moderate Taiwan earthquake is also analyzed to demonstrate the possibility of rapidly simultaneous determination on the finite fault source parameters for local earthquake. The estimated fault parameters and rupture directivity for the five earthquakes are quite consistent with those obtained by previous studies. For the 1992 Landers earthquake, which had a strike-slip mechanism, the rupture plane was clearly determined from the developed algorithm. For other events with thrust mechanism, it is difficult to determine the rupture plane, but other fault parameters were determined robustly, especially on focal mechanism. The rupture lengths and source durations of the five earthquakes have positive correlation to the seismic moment. In this study, a promising approach to determine the focal mechanism, seismic moment and rupture length of an earthquake was presented. Future efforts related to this work will focus on developing a semi-automatic data process based on the method to quickly estimate the source parameters. Further studies on this work can also provide important information on scaling of the earthquakes for better understanding of earthquake physics on rupture characteristics. Moreover, on purpose of seismic hazard assessment, this method will be efficiently applied to regional earthquakes on account of proper local velocity structure model and real-time data transmission. | en_US |