# Joint Multi-Scenario-Based Earthquake and Tsunami Hazard Assessment for Alexandria, Egypt
## 2 Seismicity, a Seismotectonic Framework, and the Impact of Tsunamigenic Sources on Alexandria  
The northern Egyptian continental margin is considered a transitional zone between continental and oceanic crusts, as indicated by [7; 17; 18; 19; 20; 21]. In this region, the stress field undergoes a shift from predominantly tensional forces on the Egyptian landmass to compressional forces along the Hellenic Arc convergence zone (see Figure 2). The Egyptian continental margin is structurally affected by three main fault trends: northwest-southeast Temsah; northeast-southwest Rosetta, and east-west fault trends (HZ) (e.g., [18; 22; 23; 24]). Alexandria is located south of the folded arc that shapes the Mediterranean Ridge [17]. This region's seafloor is occupied by significant geological features, including the Nile Deep Sea Fan, Eratosthenes Seamount, and Herodotus basin [17]. Among these features, the Nile Deep Sea Fan is the most significant accumulation of sedimentary clastic material in the Eastern Mediterranean Sea. Its boundaries are defined by the Dead Sea shear zone to the east, the Cyprus convergent zone, and the Mediterranean Ridge to the north [17]. Several geodynamical studies (e.g., [25; 26]) have indicated the northward motion of northern Nubia relative to Eurasia of about 5 mm/yr. [PERSON] and [PERSON] [27] used crustal deformation data from 16 permanent GPS stations and 47 non-permanent stations that cover Egypt during the period 2006-2012. They estimated the movement rate of northern Nubia and the interaction between the Nubia, Eurasia, and Arabia plates. Their analysis revealed a relative motion between the Nubian and Eurasian plates at a rate of approximately 6.5 \(\pm\) 1 mm/year, with an increasing trend observed towards the Hellenic trench. Throughout its history, Alexandria has been subject to varying degrees of damage caused by earthquakes and tsunamis from nearby and distant seismogenic sources. Table 1 indicates the historical and instrumental earthquakes felt in Alexandria that caused considerable damage. Figure 3a,b illustrate the seismic activity around Alexandria during the period from 2000 BCE to 2020 CE [13; 17; 28; 29; 30; 31]. These earthquakes happened at local seismogenic sources (e.g., the continental margin of Egypt) and distant seismogenic sources (e.g., Hellenic and Cyprus Arcs) from Alexandria. Many seismicity studies [12; 13; 29; 31] indicated that there were at least 25 strong earthquakes that impacted Alexandria from 320 to 2020 CE. Historical accounts of the aftermath of the earthquakes in Alexandria indicate widespread devastation, with many houses severely damaged. Tragically, the impact of ground motion and subsequent tsunami inundation resulted in injuries and the loss of thousands of lives [29; 32]. The 320, 365, 956, and 1303 CE earthquakes, among others, were severely felt and caused damage and losses in Alexandria due to ground shaking and related tsunamis. Moreover, more recent, some other earthquakes have been felt in Alexandria and have caused some damage (i.e., September 12, 1955, earthquake (6.8 Mw), May 1998 earthquake (5.5 mb), and October 2012 earthquake (5.5 Mw) [13; 17; 28; 29; 30; 32; 33; 34; 35]). These earthquakes had different epicentral distances, as indicated in Figure 3b, and occurredat different times, which we believe led to different levels of exposure and vulnerability. Nevertheless, far-source effects, e.g., in connection with the Red Sea earthquakes (e.g., 1969 earthquake, 6.9 Ms) and the Gulf of Aqaba (e.g., 1995 earthquake, 7.3 Mw), were also felt in Alexandria, with a maximum intensity of III-IV on MMS [29]. The Eastern Mediterranean (EM) region is a region prone to seismic and tsunami activity, primarily due to the Hellenic Arc. This arc, comprising the West Hellenic Arc (WHA), East Hellenic Arc (EHA), and Cyprian Arc (CA), has been identified as the source of the most significant tsunamis in the region.