## 2 Geodynamic Setting and Tectonic Pattern  
Our study area, located in Central-Eastern Macedonia (mainland Greece), belongs to the broader extensional regime which prevails after the southward migration and roll-back of the Hellenic Arc since the Early Miocene (e.g., [18; 19; 20; 21; 22]). The variously proposed (micro-) plate models for the broader Aegean and Anatolian regions (e.g., [23] and references therein) primarily suggest that Central-Eastern Macedonia lies either on an undivided Eurasian plate overthrusting the African plate and undergoing internal deformation, or on a separated Eurasian plate into smaller micro-plates, such as the stable Eurasian to the north and the Aegean and the Anatolian to the south, all overriding the African plate. The dominant structure north of the Hellenic Arc is the North Anatolian Fault (NAF) that accommodates 24-30 mm/yr of dextral motion [14; 24] and its western prolongation in the Aegean Sea, i.e., the North Aegean Trough (NAT) and, further to the west, the North Aegean Basin (NAB). Whereas NAT is a quasi-pure shear fault zone, the NAB is characterized by transenational deformation and represents a transitional region, which links pure strike-slip faulting along the NAF and pure extension in central Greece (e.g., [25; 26]). This lithospheric-scale transcurrent tectonic structure is believed by many researchers to represent the northern margin of the Aegean-Anatolian microplate(s), along which the latter slides westwards, pushing the former to the SW and affecting the surrounding area, including Macedonia and Thrace (North Greece), by forming a transenational field. The same stress field is responsible for the formation of large, tectonically controlled basins usually delimited by antithetic normal, dip-slip, tectonically active faults [18; 20; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37]. Although the favorable faulting direction is mostly E-W, i.e., perpendicular to the modern N-S-oriented extensional field (e.g., [38; 39; 40; 41; 42; 43]), NW-SE-striking active faulting is also evident, possibly reactivating the inherited extensional structures of the earlier Late Miocene to Pliocene, NE-SW-oriented extensional phase [44; 45; 41]. Palaeoseismic trenching in the Northern Mygdonia Basin, supported by radiometric dating, confirmed that both the NW-SE- and E-W-trending fault zones that bound the northwestern and northern basinal margins, respectively, are both Holocene active [46]. This is the reason why the dominant basins in Central-Eastern Macedonia (Mygdonia, Strymon, and Drama-Phillipi basins) demonstrate margins in both NW-SE and E-W directions, with the latter ones imprinted upon the former ones. Although this region is characterized by low seismicity, compared to other regions of the Aegean, a strong earthquake has been recorded. In particular, this seismic event occurred in Amphipolis (597 AD, -M6.8), while no seismic events exceeding M5.0 have been documented for the last 120 years [47; 48]. Low seismic activity in Central-Eastern Macedonia is in agreement with the low values of the geodetic strain rate. As seen in Figure 1[16], the strain rate in this area is contrastingly lower than the neighbouring NAT or NAB. The same pattern has been suggested by many other researchers as well [7; 49; 50; 51; 16; 17]. The strain tensor analysis from previous works may show some variances in the main axes' direction, but they all agree with the relatively much lower values compared to the southern parts of the Aegean [7; 8; 14; 15; 16; 17; 24; 51; 52; 53; 54; 55; 56; 57]. In particular, [PERSON] et al. [58], who focused on the Strymon basin fault system, suggested significantly higher strain values compared to the previous works, while no strain axes direction was proposed; however, even these values are lower compared to South Aegean region. Figure 1: (**a**) Map showing the location of inset map (**b**). (**b**) Map of the principal tectonic structures  
in the broader Aegean region (after [20, 25, 26, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68]).