The 1999 earthquakes (which had magnitudes Mw of 7.4 and 7.2) in Turkey caused great destruction and damage for Yalova (Turkey) sites in the Marmara Region. In the investigation area, the mainly reason for destruction is the liquefaction. As it is known, liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. In the frame of this research, probabilistic and deterministic analyses were used to determine the safety factors for several parameters. For the study area, the probabilistic seismic hazard analysis showed very high seismic activity. By using deterministic seismic hazard analysis, the magnitudes were estimated for the three rupture (with four different fault lengths, 109, 120 and 174 km) model of North Anatolian Fault Zone in the Marmara Region. By using analysis (deterministic and probabilistic), estimated magnitudes and accelerations of earthquake were taken as alternatively 6.5, 7.0 and 7.5 for magnitudes and from 0.2 - 0.50 g for accelerations. For several design earthquake parameters, cyclic stress analysis of liquefaction were applied to the field data (both SPT (N) and S wave data), obtained in the Yalova region. In the first phase of the study of liquefaction, the cyclic stress ratio approach was applied for all data to analysis of soil liquefaction. Then FS (factor of safety) values of liquefaction were estimated with this approach.