# Joint Multi-Scenario-Based Earthquake and Tsunami Hazard Assessment for Alexandria, Egypt
## 3 Multi-Scenario Physics-Based Seismic Hazard Analysis
### Far Source Effects (Long Period) at Alexandria  
Several earthquakes that were felt and that caused damage in Alexandria originated from seismogenic areas outside Egypt (e.g., Hellenic Arc, Cyprus Arc, Gulf of Aqaba, and Dead Sea) [29], as proven from recent and historical observations. The far seismic sources should not be ignored in Alexandria, given their significant magnitude and the frequency content of the ground motion they produce, particularly in the case of tall buildings in the city; the collapse of the Alexandria lighthouse due to the 1375 CE earthquake serves as a well-known example of their potential impact. A long period of ground motion could be hazardous, especially in New Alamein City, which is 35 km west of Alexandria, where many high-rise towers are under construction. Furthermore, strong earthquakes occurring in the Hellenic and Cyprus Arcs may have the potential to cause devastating tsunamis (e.g., 365 Crete earthquake, Mw = 8.5; 1222 Cyprus earthquake, Mw = 7.5; 1303 Rhodes earthquake, Mw = 8.5), as indicated by [PERSON] et al. [2]. Recent examples are the events of 12 September 1955 (north Egyptian pacific margin, Mw = 6.8), 31 March 1969 (Northern Red Sea, Mw = 6.9), 22 November 1995 (Gulf of Aqaba, Ms = 7.3) and 9 October 1996 (southern Cyprus, Mw = 7.0), which were felt in Alexandria at epicentral distances larger than 300 km [13]. On the other hand, the 320, 365, 956, and 1303 CE events are the most significant historical earthquakes with magnitudes larger than 7. Based on the intensity data and damage pattern information provided by [PERSON] et al. [13] and [PERSON] and [PERSON] [36] for the 1303 earthquake, [PERSON] et al. [29] suggested that two different earthquakes hit the city on the same day--one earthquake from a local source (Al Fayoum area) and another earthquake from a far event located in the Hellenic Arc. They supported this suggestion by attributing the collapse of the top of the ancient lighthouse of Alexandria, the slow ground motion that made people walk with difficulties, and the duration of shaking that lasted for several minutes to the long period effect from the far source, which nucleated in the Hellenic Arc. The local event was suggested to be in El-Fayoum, which caused short-period effects to be reported, e.g., the complete and heavy damage reported in Cairo and Nile Delta, including the public buildings that were usually of good quality, the way people felt the earthquake, the movement of the water in the Nile, and the rock falling and landslides near Minya.  
The ground motion intensities (e.g., PGA, PGV, and PGD) were computed for the 1303 earthquake in order to investigate and verify whether the strong earthquakes that originated in the Hellenic Arc could significantly cause damage in Alexandria. According to [PERSON] et al. [16] and [PERSON] and [PERSON] [35], the August 1303 earthquake, with I\({}_{0}\) = X Mw = 8.5, originated in the Hellenic Arc 600 km away from the Egyptian coasts at 25.63\({}^{\circ}\) E and 35.18\({}^{\circ}\) N, which caused widespread damage in the Eastern Mediterranean region. The 1D-crustal modal (Figure 6) and source parameters of 1303 earthquakes, which are listed in Table 2, were used to compute the synthetic seismograms at Alexandria. The shaking lasted more than 4 min, and the computed peak ground motion at Alexandria was 6 cm/s\({}^{2}\), 4 cm/s, and 18 cm for PGA, PGV, and PGD, respectively. Based on these results, we can support part of the conclusions by [PERSON] et al. [29], who proposed that the reported damage in Egypt was related to a local earthquake.