Propagation and termination of a strike slip fault in an extensional domain: The westward growth of the North Anatolian Fault into the Aegean Sea

Geometry and kinematics of the active submarine faults over the North Aegean Trough, a complex and highly deforming boundary zone between the Eurasian and the Anatolian/Aegean micro-plates, were examined to investigate how a strike slip motion propagates through an extensional domain. The bathymetric and seismic reflection data analysis show, that the investigated area is affected from east to west, by three sets of active faults striking ENE-WSW, NE-SW and WNW-ESE. The ENE-WSW and NE-SW striking faults are right lateral strike slip faults and are considered strands of the northern branch of the North Anatolian Fault into the north Aegean Sea. The former set bounds the Saros basin and the latter set occupies the eastern and central part of the Sporades Basin in the eastern and western parts of the North Aegean Trough, respectively. The WNW-ESE striking faults are normal low angle faults and develop at the western parts of the Sporades Basin. It is suggested that the strike-slip fault system advances westwards and when it reaches the 23.8°E meridian, its right lateral motion is transferred to the WNW-ESE normal faults system, forming a 70 km wide normal faulting zone through which the shear is distributed. The interaction between the strike slip and normal faults probably started with the arrival of the northern branch of the North Anatolian Fault into the western part of the Sporades Basin since 430 ka BP (Marine Isotopic Stage, 12). The described fault architecture and their spatial distribution in the North Aegean Trough are consistent with: (i) the earthquake fault plane solutions and (ii) the stress and strain pattern prevailing across the area. Furthermore, all these three provide evidence that the northern branch of the North Anatolian Fault terminates at the western end of the NAT and does not continue to central Greece.