The earthquakes near Chirpan and Plovdiv, Bulgaria, occurring on April 14 (Ms 6.8) and 18, 1928 (Ms 7.0), respectively, represent significant seismic events in the region's history. These events are unique because geodetic measurements were carried out before and after the earthquakes. This study aims to evaluate the effects of the fault parameters on the focal mechanism solutions in respect to the observed displacements. The analysis utilizes the Okada model to calculate movements over the fault area testing different parameters. The focal mechanisms of the two events underwent parametric testing, with variations in the exploration of fault dip, rake and geometry. The contribution of each parameter was evaluated. Modelled solutions were compared with observations in order to understand the dynamic behavior of the media during seismic events. To enhance the accuracy of dislocation modelling across the fault, its length was divided into several segments. The applied approach provides an improved representation of real observations and dislocations.