The horizontal velocity field in the deforming Aegean Sea region determined from the moment tensors of earthquakes

The spatial distribution of seismic moment tensors of earthquakes in the Aegean region over the time interval 1909-1983 are used to recover a continuous horizontal velocity field that describes the overall deformation of the lithosphere at large length scales. The calculated velocity field is dominated by two effects: 1) an E-W right-lateral shear of the eastern Aegean, related to motion on the North Anatolian fault becoming distributed as it enters the Aegean; and 2) a N-S extension, probably related to the sinking of the slab in the Hellenic Trench. A comparison of paleomagnetic declination data with the expected rotation of rigid elongate inclusions in the velocity field shows in most places an agreement in sense and approximate agreement in rate of rotation. The velocity field obtained preserves the strike directions of the major faults as directions of zero length change, in spite of considerable smoothing. This observation is used to speculate that the interaction between the upper crust and the rest of the lithosphere beneath it may involve an interplay of effects. -from Authors