The North Anatolian Fault accommodates most of the motion between the Eurasian plate and the apparently little-deforming, interior of central Turkey (Anatolian Block). Therefore, the direction of overall slip across this zone is crucial. I use teleseismic long-peniod P- and SH- waveforms to determine the source parameters of the four largest earthquakes that occurred in, or near, the North Anatolian Fault Zone during 1999 August-November Golcuk-Duzce sequence, along with the study of Taymaz et al. (1991). These mechanisms show that the faulting during the largest shocks is mostly right-lateral strike-slip in nature, on almost East-West striking planes and with slip vectors directed East. The others have both strike-slip and normal faulting mechanisms. Combined seismological, geological and geomorphological observations are consistent, and suggest that slip-partitioning on the western part of North Anatolian Fault is still taking place. The westernmost continuation of North Anatolian Fault (NAF) into the Sea of Marmara still requires further investigations to better understand the complexity of faulting associated with earthquakes.