# Joint Multi-Scenario-Based Earthquake and Tsunami Hazard Assessment for Alexandria, Egypt
## 5 Discussion and Conclusions  
In our study, we utilized the NDSHA approach to investigate the seismic hazard in Alexandria on an urban scale. Our analysis included available information on seismogenic zones, levels of seismicity, and lithospheric geophysical properties, enabling us to compute physics-based synthetic seismograms and map them for observation sites across the study area. This study applied up-to-date seismogenic zones and earthquake catalogs (magnitude of 5.0 and more significant for the period 320-2020) for ground motion computations. The seismic engineering parameters (e.g., PGD, PGV, PGA, and spectral accelerations) that could be used to express the level of seismic hazard in a specific area can be easily extracted from these synthetic seismograms. Our study reveals that the northeastern region of Alexandria is characterized by moderate to high seismic hazards, particularly from sources originating in the Mediterranean Sea. The maximum ground acceleration in this area is estimated to be 0.15 g. By contrast, other parts of the city exhibit relatively lower seismic hazards. Previous studies, including [PERSON] et al. (2012), reported maximum spectral acceleration (Sa) values of 0.03 g, 0.10 g, and 0.25 g for the spectral period of 0.1 s and return periods of 72, 475, and 2475 years, respectively, in Alexandria. Additionally, [PERSON] et al. (2017) provided peak ground acceleration (PGA), Sa (0.1 s), and Sa (0.2 s) values of 0.09 g, 0.23 g, and 0.20 g, respectively, for a return period of 475 years. Seismic risk analysis for Alexandria was conducted by [PERSON] et al. (2011), who estimated the percentage of expected damage to constructions to be around 2.2%, with 19% injuries and 0.01% fatalities. The study also identified the Al Montazah, Al Amereya, and Bab Sharq districts as having the highest seismic risk compared to other districts in Alexandria. We also conducted a comprehensive tsunami inundation assessment for the Alexandria coastline by employing empirical relations based on average and maximum tsunami wave amplitude values for nine potential tsunamigenic earthquake scenarios taken from work by [PERSON] et al. (2013). We integrated information on the tsunami wave amplitude obtained for individual scenarios to create an aggregated scenario representing the maximum and mean expected wave amplitudes. An average ETA for the Hellenic and Cyprus Arc sources was also mapped, and its value for a tsunami in Alexandria falls within the range of 75-80 min. The aggregated inundation map shows that the districts of Al Gomrok and Al Montazah are the most vulnerable areas in Alexandria in the event of a tsunami. The western part of the city, known as Al Sahel Al Shamally, is less vulnerable to the impacts of a tsunami than the eastern side due to natural protection afforded by a ridge of carbonate material that runs parallel to the shoreline. However, it is essential to note that the water canals in this area could still contribute to the cascading of hazards. Alexandria's susceptibility to local and regional earthquakes, which could trigger tsunamis and cause geological hazards on both land and sea, can have catastrophic economic and social consequences if each risk is addressed independently without considering their combined impact. It is crucial to study these hazards comprehensively and on an integrative basis. Also, visualization of multiple hazard assessment parameters is critical for developing effective and practical emergency response plans, enhancing public awareness, and implementing protective measures. In this sense, Figure 14 displays an example of joint earthquake and tsunami hazard maps that can be valuable in the future if combined with high-resolution exposure and vulnerability models for multi-risk assessments for Alexandria. The joint earthquake and tsunami inundation maps, created using a GIS, show the peak ground acceleration and inundation depth resulting from various earthquake and tsunami scenarios at specific locations.