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SUMMARY Gephart & Forsyth’s method has been applied to estimate stress orientations from earthquake fault-plane solutions of the westernmost North Anatolian Fault zone (NAFZ), its westward continuation in the Northern Aegean Sea, where it interacts with the normal faulting of central Greece, and of the western coastal parts of Anatolia. In total, 163 fault-plane solutions were used to invert for the stress tensor of 9 seismotectonic subregions. Magnitudes range from 1.1 to 7.4. All events have shallow focal depths; most occurred in the uppermost 15 km and very few in the 15 to 40 km depth range. The region studied is characterized by strike-slip (NAFZ), by transtension (Central Greece and western Anatolia) and by a strong signature of transpression in the Marmara area. From NAFZ to central Greece, the σ3 axis changes, continuously and smoothly, its orientation from N35 ◦ E in the westernmost NAFZ to nearly North‐South in continental central Greece, and the maximum horizontal stress, σHmax changes from WNW‐ESE to ∼E‐W. The total angle of lateral variation in the direction of either σHmax or σ3 is ∼40 ◦ . In central western Anatolia the orientation of σ3 is NNE‐SSW (N10 ◦ E) while in southern western Anatolia it is NNW‐SSE (N33 ◦ W). In both cases the development of the major grabens (Simav, Gediz, Menderes) is in agreement with the resolved stress tensor. At the termination of the NAFZ against central Greece the regime is complex. The dextral shear motion transferred from the east crosses the Pilion peninsula and northern Evia Island where it interacts with the major normal faults of continental Greece. These faults have variable orientations. The E‐W trending Quaternary fault system and the NW‐SE trending fault system, which is inherited from the past. The latter faults under the presently acting stress field are reactivated either as strike-slip faults with sinistral strike-slip component (when oriented at small angle in respect to σ3) or as normal faults with small sinistral strike-slip component (when oriented at high angle in respect to σ3). The occurrence of the recent 2001 July 26 Skyros event, which was clearly connected to a NNW‐SSE fault with sinistral strike-slip motion, provides strong seismological evidence that the old structures can equally well be reactivated under the presently active stress field.

SUMMARY A procedure for the analysis of data, concerning seismic moment release and fault-plane solutions, for the estimation of active crustal deformation is proposed. The formulation takes advantage of all the available historical and instrumental data for the calculation of the 'size' of the deformation in a seismic zone and of all the reliable fault-plane solutions which are available for a broader seismic belt for the determination of the 'shape' of the deformation. A detailed analysis of the errors involved in each parameter, based on a Monte Carlo numerical method, is suggested. The proposed procedure is applied to a region of extensional tectonics in central Greece. The resulting seismic strain rates show that the dominant mode of deformation in the area is extension at a rate of the order of 6 mm yr-' and a mean azimuth of N25"W. A vertical contraction rate of about 1 mm yr-' has also been calculated. The results from geodetic measurements performed by Billiris et al. (1991) declare that the calculated seismic deformation represents about 60 per cent of the total strain of this area.

SUMMARY The source parameters of the recent 1983 January 17 Ionian island event are obtained by the inversion of body waves. An optimum source depth of 8 km is determined and the source parameters of the major double couple are: strike = 60°, dip = 47°, rake = 174° and seismic moment M0= 7.3 × 1025 dyne cm. This mechanism implies a strike-slip dextral fault with a small thrust component. This solution ascertains the existence of a transform fault connecting the northwestern edge of the Hellenic are with the compressional zone which is produced by the collision of the Apulian plate with the Eurasian plate along the Adriatic-north Ionian coast. This right lateral strike-slip fault probably terminates the Hellenic subduction zone.