One of the most important challenges in seismic evaluation of structures comes from wide variability of possible motions that a specific site may experience. This variability arises from the intrinsic randomness of seismic motions (aleatory uncertainty) and lack of knowledge about the physical process behind an earthquake (epistemic uncertainty). The epistemic uncertainty in estimating ground motion can be properly characterized by providing an understanding of the physical aspects of earthquake source models. In this paper, a combination of the theoretical-based Green’s function method and hybrid slip source model is used to reducethesource uncertainty. The procedure is implemented on the 1994 Northridge earthquake as a case study. For this purpose, the method is validated against recordings stations through demonstrating a good agreement between the elastic response spectra corresponding to the simulated and recorded data, confirming the reliability of the procedure. A simple additive weighting algorithm is used to select the best fit amongst simulated waveforms and optimal source model.
