## 3 Seismic Hazard in the East Anatolia and the 6 February 2023 Earthquakes  
Turkey is among the most earthquake-prone countries in the world, suffering from earthquakes with Mw \(\geq\) 5.5 almost on a yearly basis [22], events characterized by high potential for adverse effects on the built environment and the population. The North Anatolian and the East Anatolian Fault Zones are major earthquake tectonic structures that are responsible for the generation of many damaging earthquakes not only during antiquity and the historical period but also during the period of instrumental recordings [23; 24]. The high level of seismic hazard in Turkey could be highlighted by the recent generation of destructive earthquakes with Mw \(\geq\) 6.0, namely the 24 January 2020 Mw = 6.8 Elazig earthquake [25; 26], the 30 October 2020, Mw = 7.0 Samos earthquake [27; 28; 29; 30] and the 23 November 2022 Mw = 6.1 Duzce earthquake [31]. Many other seismic events have occurred in the past and are among the largest and most destructive earthquakes worldwide such as the 17 August 1999, Mw = 7.6 Izmit earthquake [32; 33], among others. The EAFZ constitutes a left-lateral transform plate boundary, which dominates East Anatolia and greatly affects the geodynamics and active tectonics in the area [24; 34; 35; 36]. It extends from Karlova Triple Junction in the north, where it meets with the North Anatolian Fault Zone, to Antakya in the south, where it joins to the Dead Sea Fault, and constitutes a complex boundary separating the Anatolian plate located northwestwards from the Arabian plate located southeastwards [24; 36]. Its western part constitutes a 65 km wide deformation zone which comprises two strands: the northern and the main which are also segmented [24]. The main strand of the EAFZ is composed of seven segments, includingthe Erkenek, Pazarcik, and Amanos segments [24]. The northern strand has an average E-W direction, while close to its eastern termination its strike changes from E-W to NE-SW. The E-W striking fault system is structured by the Surgu and Cardak segments, while the western part of the northern strand comprises eight segments [24]. The EAFZ constitutes the main damaging earthquake source in the East Anatolia. It has been characterized by considerable earthquake hazards in the past and many destructive earthquakes occurred on the fault zone during the historical and instrumental period with extensive damage on the built environment and great loss of life [24; 35; 37; 38] The EAFZ seems to be more active in the 21 st century with the occurrence of the 27 June 1998, Mw = 6.3 Adana-Ceylan earthquake [39], the 1 May 2003, Mw = 6.4 Bingol earthquake [40], the 8 March 2010, Mw = 6.1 Basyurt (Elazg) earthquake [41], the 23 October 2011, Mw = 7.1 Van earthquake [42] and the 24 January 2020, Mw = 6.8 Elazg earthquake [38]. These events highlighted the seismic hazard of the East Anatolia. On 6 February 2023, East Anatolia was hit by two devastating earthquakes. The epicenter of the first major shock was located at a distance of 37 km west-northwest of Gaziantep city according to the related information provided by the US Geological Survey [9] (Figure 1). It was a shallow event, with a focal depth of 12 km [43] and it was caused by the rupture of a NE-SW striking near-vertical left-lateral strike-slip fault according to the related information provided by several seismological institutes and observatories [44]. The properties of the Mw = 7.8 earthquake as well as its focal mechanism are consistent with the events that occurred along or close to the EAFZ and the Dead Sea Fault Zone, which accommodates the westward extrusion of the Anatolia plate into the Aegean Sea region and the northward motion of the Arabian plate relative to the Africa and Eurasia plates respectively (Figure 1). An Mw = 6.7 aftershock followed 11 min after the generation of the first shock, while 9 h later a new major earthquake was generated along the EAFZ.