Local Vertical Crustal Movements in the Mygdonian Basin - North Greece, Resulting from Gravity and GPS Measurements

Repeated gravity measurements in the tectonically active Mygdonian basin, close to Thessaloniki North Greece, showed gravity changes ranging from 420 to 810 nm s(-2) within a period of 20 years. These gravity changes, which were interpreted as local vertical crustal movements, using the free-air relation, correspond to changes front -26 to 13 cm. The rate of the gravity (and correspondingly height) change is higher in the rebound period, after the 1978 seismic sequence near Thessaloniki. The rate of the vertical changes estimated from the gravimetric observations was compared with corresponding rate estimated from GPS measurements. Conclusions were drawn, concerning the fault system of the region.