A GNSS network of 36 points was established in 2006 in the eastern part of the North Anatolian Fault Zone, which is located between Tokat and Erzincan. GNSS measurements were made in 2006-2008 in the Kelkit valley and these points' velocities were calculated. This study compares GNSS velocities estimated with different datum definitions and the effects on fault locking depth and strike-slip rates, which are parameters of elastic rebound theory. These two parameters contain preliminary information on possible earthquakes in the region. An average slip rate of 21 mm/year and a locking depth of 12,72 km are estimated.