Fault structure and related basins of the North Aegean Sea and its surroundings

Abstract

Fault structure and basin evolution in the northern Aegean Sea and its surroundings have been investigated using bathymetry, available onshore and offshore seismic profiles, onshore fault patterns from NE Greece, NW Turkey, three islands in the Aegean Sea, surface ruptures associated with the, 1978 Thessaloniki earthquakes, GPS measurements from North Aegean Islands and a number of earthquake focal plane solutions, and historic seismicity. Bathymetric and isopach data show that the North Aegean Trough can be divided into the Sporades basin and the Saros Trough. Post‐Miocene sediment thickness differences in these basins, offset of distinct horizons, and frequent seismicity along basin‐bounding faults indicate that sediment accumulation in the area is fault controlled. Offshore seismic profiles show that the basin‐bounding faults are dominantly characterized by apparent normal components as well as strike‐slip components inferred from typical fault zone profiles. Additional evidence for existence of strike‐slip faulting comes from earthquake focal plane solutions. We refined the pattern and kinematics of the faults controlling the basins and classified them into two major groups. The faults in the first group trend NE‐SW and ENE‐WSW and are here interpreted to be dominantly right‐lateral strike slip with normal or reverse components. These faults accommodate a similar amount of deformation like the Ganos fault and thus represent the westernmost extension of the North Anatolian fault zone. The faults in the second group trend NW‐SE and are dominantly normal faults with an occasional left‐lateral component. These faults are believed to manifest the termination of the North Anatolian fault zone. Because of the segmentation of the right‐lateral strike‐slip faults and the preexisting NE trending tectonic grain, the basins are compartmentalized into smaller depocenters. Basins are orientated with their long axes either parallel to the NE‐SW to ENE‐WSW trending echelon strike‐slip faults, or, in the zone north of the strike‐slip faults parallel to the NW‐SE trending normal faults. The interpretations regarding the kinematics of the faults are consistent with the data compiled from the islands near the faults and from the land in NE Greece and NW Turkey. The northern Aegean basins and their spatial relationships to the fault architecture representing the diffused termination of the North Anatolian fault system are consistent with the mechanical principles of the strike‐slip tectonics.