Deterministic tsunamigenic earthquake hazard assessment for the northern coast of Egypt based on multi-scenario approach

Egypt’s northern coast can be considered a dynamic natural system like several coastal regions worldwide. While it provides many opportunities and resources, it may also pose significant challenges to the community, as the area is prone to land and marine-related geohazards (e.g., earthquakes, sea-level rise, land subsidence, storms, coastal erosion, and tsunamis). Also, the recent national census survey indicates that numerous assets, systems, infrastructures, and cultural heritage sites (elements under risk) are situated within the zone of hazards. Multi-hazard and risk assessments are therefore necessary to achieve national sustainable development plans. This study, in particular, focuses on tsunami hazard, which is defined here as the envelope (upper bound estimate) from a comprehensive set of possible simulated tsunami scenarios. The main aim of this work is to provide robust and conservative hazard estimates while considering the variability related to earthquake parameters. The seismological parameters that describe each tsunamigenic earthquake scenario are extracted from published works. Also, detailed nested grids of topo-bathymetry are developed from free-access data sources. The seismological and topo-bathymetry data are essential components for separately carrying out tsunami modelling for each individual scenario. The simulated scenarios are aggregated to build tsunami intensity maps of interest. The ETAs (Expected Time of Arrival), the maximum, average, and standard deviation of coastal tsunami wave height and the inundation maps are developed based on an aggregated scenario. In addition, the simulation of tsunami wave propagation can provide synthetic mareographs computed at selected sites, which can be used for detailed site-specific analysis. The obtained results from the current work indicate that the northern Egyptian coast is characterized by a moderate-to-high tsunami hazard. The western part of this coast poses the maximum coastal tsunami wave heights; however, the longitudinal dunes, extending parallel to the shoreline, form a natural barrier that reduces the tsunami hazard. In contrast, the central and eastern parts of the Nile Delta and the entrance of the Suez Canal show relatively lower tsunami amplitude but a large inundation because of its low altitude and flat topography that could pose a higher risk to this area. The relatively high exposure and high vulnerability of elements under threat along the northern coast of Egypt may dramatically increase the future risk. It is critical to incorporate these results into a broader multi-hazard and risk assessment to effectively mitigate the impact of natural disasters on the Egyptian-Mediterranean coast. © 2023, The Author(s), under exclusive licence to Springer Nature Switzerland AG.