A new approach to the structural features of the Aegean Sea: Cellular neural network Davut Aydogan 1, *, Ali Elmas 2 , A. Muhittin Albora 1 and Osman N. Ucan 3 1 Department of Geophysics, Engineering Faculty, Istanbul University, 34850 Avcilar, Istanbul, Turkey 2 Department of Geology, Engineering Faculty, Istanbul University, 34850 Avcilar, Istanbul, Turkey 3 Department of Electric & Electronics, Engineering Faculty, Istanbul University, 34850 Avcilar, Istanbul, Turkey *Author for correspondence: E-mail: aydogan@istanbul.edu.tr Received 24 February 2004, accepted 26 December 2004 Key words: cellular neural network method, edge detection, gravity anomaly, tectonic, Aegean Sea Abstract In this study, structural features in the Aegean Sea were investigated by application of Cellular Neural Network (CNN) and Cross- Correlation methods to the gravity anomaly map. CNN is a stochastic image processing technique, which is based on template optimi- zation using neighbourhood relationships of pixels, and probabilistic properties of two-Dimensional (2-D) input data. The performance of CNN can be evaluated by various interesting real applications in geophysics such as edge detection, data enhancement and separa- tion of regional/residual potential anomaly maps. In this study, CNN is used in edge detection of geological bodies closer to the sur- face, which are masked by other structures with various depths and dimensions. CNN was first tested for (prismatic) synthetic examples and satisfactory results were obtained. Subsequently, CNN/Cross-Correlation maps and bathymetric features were evaluated together to obtain a new structural map for most of the Aegean Sea. In our structural map, the locations of the faults and basins are generally in accordance with the previous maps from restricted areas based on seismic data. In the southern and southeastern parts of the Aegean Sea, E–W trending faults cut NE–SW trending basins and faults, similar to on-shore Western Anatolia. Also, in the wes- tern, central and northern parts of the Aegean Sea, all of these structures are truncated by NE-trending faults. Introduction The Aegean region (Figure 1) represents a broad zone of extension (Phillipson, 1910–1915) and includes the western end of the right-lateral North Anatolian Fault Zone which separates the Anato- lian Block from the Eurasian plate (McKenzie, 1972; Ginzburg et al., 1987; Taymaz et al., 1991; Armijo et al., 1996). The northern and central parts of Aegean Sea are influenced by the North Anato- lian Fault (Armijo et al., 1999; Koukouvelas and Aydin, 2002), whereas in the southern part of Aegean Sea the Hellenic subduction zone has played a dominant role (McKenzie, 1972; Le Pichon and Angelier, 1981; Walcott and White, 1998). The north–south extension in the Aegean region has been explained by three main models: (1) roll-back of the subducted slab beneath the southern Aegean (Le Pichon and Angelier, 1979); (2) by the collision of Arabian Plate with Eurasia during the Middle Miocene, causing westward escape of the Anatolian Plate and southwestward motion of the southern Aegean (McKenzie, 1972; Dewey and Sengor, 1979); (3) gravitational collapse of over-thickened continental crust (Dewey, 1988). Most of the Aegean extensional region is under the sea and thus difficult to observe. Therefore, various methods have been used for understanding of the structural features of the Aegean Sea. A ser- ies of publications revealed that the Aegean Sea has complex structural features (Dewey and Sen- gor, 1979; Mercier et al., 1979; Le Pichon and Angelier, 1979; Papazachos et al., 1984; Jackson, 1994; Armijo et al., 1996; Papazachos and Kiratzi, 1996; Hatzfeld, 1999; McClusky et al., 2000; Koukouvelas and Aydin, 2002). Recent studies of the seismicity and off-shore seismic profiles in the Aegean Sea indicate the existence of two main types of faulting; normal faulting and strike-slip faulting (Kiratzi et al., 1991; Taymaz et al., 1991; Armijo et al., 1996; Gautier et al., 1999; Ko- ukouvelas and Aydin, 2002; Kiratzi and Louvari, Marine Geophysical Researches (2005) 26: 1–15 Ó Springer 2005 DOI 10.1007/s11001-004-8216-7