Northern Greece is an intracontinental region behind the Hellenic subduction zone, with widespread seismic activity (ranging from low to high), with strong destructive earthquakes of M ≥ 6.0 in historical to recent times. Geological and seismological data indicate that recent seismic activity is mainly localized along large, inherited, fault zones, which have transected Northern Greece since Oligocene-Miocene times. The main active fault zones in Thrace, and Eastern and Central Macedonia strike approximately east-west, with lengths of 40–120 km. Fault segments strike WNW-ESE to ENE-WSW and range from 10 to 30 km in length. In Western Macedonia the main active fault zones strike NE-SW to ENE-WSW with lengths of 40–60 km and consist of 10–30 km segments. The region’s strong earthquakes are usually associated with reactivation of these fault segments and are estimated at M = 5.6–6.5. Focal mechanisms and fault-slip data from the fault zones indicate a change in the trend of extension axes from NNE-SSW in Eastern Macedonia-Thrace to NNW-SSE in Western Macedonia. Thus, neotectonic and seismological data suggest that variations in fault patterns, as determined from the large inherited fault zones transecting Northern Greece, are the major factor governing this change in the trend of maximum extension. This interpretation is consistent with the long-lived arcuate shape of the Hellenic subduction zone.

Several depocentres have developed along the NNW–SSE-striking Strouma (Strymon) Lineament since the Miocene, forming the Strouma/Strymon graben system. Some of these basins, including the Dzherman and Simitli, strike at high angles to the lineament. The rhomboid-shaped Simitli basin is limited in the south by the NE–SW-striking, seismically active Kroupnik fault and contains terrestrial clastic sediments, which have been deposited since the Sarmatian. Its formation is attributed to ‘wrench-dominated transtension’ (D _B event) which activated the basin's NE–SW-striking boundary faults as left-lateral strike-slip structures during the Early–Middle Miocene. This deformation was associated with NNE–SSW contraction and WNW–ESE extension and succeeded the NNE–SSW contraction caused by ‘pure shear-dominated transpression’ (D _A event), which governed the region in Late Oligocene–Early Miocene times. During the Middle–Late Miocene, the D _B event was followed by WNW–ESE ‘pure shear-dominated extension’ (D ₁ event), which caused further widening of the basin. The transtensional origin of the Simitli basin is explained by lateral extrusion of the crustal mass squeezed between the Apulian–Adriatic microplate and the European foreland towards the North Aegean Sea. The subduction retreat of the Hellenic orogen possibly enhanced this lateral extrusion, and from the Late Miocene onwards the NE–SW-oriented back-arc extension balanced the continuing retreat.