Discrimination of fault planes from auxiliary planes using a very dense network is important in order to improve our understanding of different fault systems. Marmara Region has the greatest importance in Turkey, having high risk of a M≥7.0 earthquake in the next 20 years. More than 6000 earthquakes have been recorded in the region for the last 5 years with M≥1.0. In this study these local earthquakes are analysed and for each cluster, and principal stress axes and fault plane solutions are determined. Relocations of the earthquakes are done by the Hypocenter software, whether Focmec software and the program of Horiuchi et al, 1995 are chosen to determine the source mechanisms. Data from 90 BB, 5 OBS and 15 SP stations at the time interval of 2006.09.02-2011.03.31 are utilized to analyse the earthquakes with ML≥2.0. Up to now, Gemlik and Yalova regions have been studied. With the criteria of minimum 10 P wave first motion polarities and maximum 1 inconsistent station, 63 and 102 source mechanisms were obtained for Gemlik and Yalova clusters, respectively. Average number of polarity measurements is 24 with a maximum of 63, with average horizontal error of 1.1, vertical error of 2.9, and azimuthal gap in station coverage is 78 degree. Additionally, 5 degree of grid search was used through the program of Horiuchi et al, 1995. Results indicate that Gemlik and Yalova regions have NE-SW trending transtensional stress regimes locating in a pull-apart basin. The processing for Cinarcik Basin is still continuing. Having a close relationship with Yalova Region as they were attributed as the two branches of the western part of the North Anatolian Fault Zone, the analysis of Cinarcik Basin will most probably lead to interesting interpretations. Moreover, western and middle Marmara regions are aimed to be analysed. In summary, detailed analysis results of large number of fault plane solutions in the Marmara Region with a new data set will be presented by this research.