In this study the spatial variations of the Plio-Quaternary tectonic activity and deformation of different fault segments of the North Anatolian Fault Zone (NAFZ) in the eastern Marmara region around Lake Sapanca, are assessed using geomorphic, morphometric and bathymetric approaches. Lake Sapanca is an E-W-trending structure located in the Izmit-Sapanca Corridor. This region is bounded to the north and to the south by the series of mountain ranges. Geomorphic and morphometric data provide evidence for variations between the two mountain front faults regarding levels of tectonic activity. These studies suggest a relatively high degree of tectonic activity along the Sapanca front in the south, in contrast with a low degree of tectonic activity along the E me front in the north of the study area. This pattern is also consistent with field evidence and seismic data of the study area. Bathymetric profiles of the lake show that the lake basin consists of different fault segments that slipped in the 1999 Kocaeli earthquake. All these data suggest that the Izmit-Sapanca Corridor is an asymmetric pull-apart basin associated with displacement along the NAFZ in the Late Pliocene. Lake Sapanca also occurs as a pull-apart basin created by the cross-basin fault of the asymmetric pull-apart basin in the Middle Pleistocene.