# Joint Multi-Scenario-Based Earthquake and Tsunami Hazard Assessment for Alexandria, Egypt
###### Abstract  
The available historical documents for the city of Alexandria indicate that it was damaged to varying degrees by several (historical and instrumentally recorded) earthquakes and by highly destructive stunamis reported at some places along the Mediterranean coast. In this work, we applied the neo-deterministic seismic hazard analysis (NDSHA) approach to the Alexandria metropolitan area, estimating ground motion intensity parameters, e.g., peak ground displacement (PGD), peak ground velocity (PGV), peak ground acceleration (PGA), and spectral response, at selected rock sites. The results of this NDSHA zonation at a subregional/urban scale, which can be directly used as seismic input for engineering analysis, indicate a relatively high seismic hazard in the Alexandria region (e.g., 0.15 g), and they can provide an essential knowledge base for detailed and comprehensive seismic microzonation studies at an urban scale. Additionally, we established detailed tsunami hazard inundation maps for Alexandria Governorate based on empirical relations and considering various Manning's Roughness Coefficients. Across all the considered scenarios, the average estimated time of arrival (ETA) of tsunami waves for Alexandria was 75-80 min. According to this study, the most affected sites in Alexandria are those belonging to the districts of Al Gomrok and Al Montazah. The west of the city, called Al Sahel Al Shambally, is less affected than the east, as it is protected by a carbonate ridge parallel to the coastline. Finally, we emphasize the direct applicability of our study to urban planning and risk management in Alexandria. Our study can contribute to identifying vulnerable areas, prioritizing mitigation measures, informing land-use planning and building codes, and enhancing multi-hazard risk analysis and early warning systems. multi-scenario hazard analysis; seismic and tsunami hazards; NDSHA; Mediterranean Sea; Alexandria 2020 13 December 2024 16 December  
plate boundary is characterized by complex geodynamics that trigger large earthquakes and tsunamis. It has several cultural heritage sites with significant historical and cultural value. These sites include, but are not limited to, the Qaitbay Citadel, the Catacombs of Kom El Shoqafa, and the Roman Amphitheater. Protecting these heritage sites from potential hazards such as earthquakes and tsunamis is crucial. In fact, by understanding the specific hazards and their potential impact on cultural heritage, experts can design and implement structural reinforcements, retrofitting measures, and emergency response plans to safeguard these sites. Alexandria is highly exposed to natural and climate-change-related hazards (e.g., floods, earthquakes, tsunamis, and sea level rise). The city was affected by strong earthquakes and tsunamis throughout its history, causing significant damage and casualties. It is worth noting that highly destructive tsunamis have been reported in some places along the Mediterranean coastline, but only some of them are known and proven to have impacted Alexandria [1; 2; 3]. Numerous studies have investigated earthquake [4; 5; 6; 7; 8] and tsunami [2; 3; 9] hazards in Egypt. However, while these studies have focused on individual hazards, it is important to note that some regions are exposed to both risks, necessitating a comprehensive approach to addressing both hazards. Few studies have been conducted to assess earthquake and tsunami hazards and risks for Alexandria, using either a deterministic or scenario-based approach (e.g., [2; 10]) or probabilistic approaches (e.g., [11; 12]). Despite the importance and profound challenges faced by the city, detailed joint earthquake and tsunami hazard assessment studies (e.g., earthquake and tsunami) have never been conducted on the city scale.