The GPS strain rate field in the Aegean Sea and western Anatolia

The GPS velocity field of the Aegean Sea and western Anatolia is used to de termine crustal deformation strain rates for the period 1988 to 1996. The z one from the Marmara Sea to the North Aegean Trough is associated with stro ng right-lateral shear motion, with maximum strain rates of 170 nstrain/a. In the northern Aegean Sea the extensional deviatoric axes are oriented NNE -SSW, associated with strain rates reaching 150 nstrain/a, and in western A natolia varying around N-S with rates of up to 95 nstrain/a. The extensiona l areas mostly coincide with active graben features. The south-western Aege an Sea is almost strain-free. In general, the areas of high geodetic strain rates are accompanied by distinct seismic clusters whereas the strain-free regions are nearly aseismic.