Abstract
Abstract. Alexandria is the second biggest city in Egypt with regards to population, is a key economic area in northern Africa and has very important tourist activity. Historical records indicate that it was severely affected by a number of tsunami events. In this work we assess the tsunami hazard by running numerical simulations of tsunami impact in Alexandria through the worst-case credible tsunami scenario analysis (WCTSA). We identify three main seismic sources: the western Hellenic Arc (WHA – reference event AD 365, Mw = 8.5), the eastern Hellenic Arc (EHA – reference event 1303, Mw = 8.0) and the Cyprus Arc (CA – hypothetical scenario earthquake with Mw = 8.0), inferred from the tectonic setting and from historical tsunami catalogues. All numerical simulations are carried out in two sea level conditions (mean sea level and maximum high-tide sea level) by means of the code UBO-TSUFD, developed and maintained by the Tsunami Research Team of the University of Bologna. Relevant tsunami metrics are computed for each scenario and then used to build aggregated fields such as the maximum flood depth and the maximum inundation area. We find that the case that produces the most relevant flooding in Alexandria is the EHA scenario, with wave heights up to 4 m. The aggregate fields are used for a building vulnerability assessment according to a methodology developed in the framework of the EU-FP6 project SCHEMA and further refined in this study, based on the adoption of a suitable building damage matrix and on water inundation depth. It is found that in the districts of El Dekhila and Al Amriyah, to the south-west of the port of Dekhila, over 12 000 (13 400 in the case of maximum high tide) buildings could be affected and hundreds of them could sustain damaging consequences, ranging from critical damage to total collapse. It is also found that in the same districts tsunami inundation covers an area of about 15 km2, resulting in more than 150 000 (165 000 in the case of maximum high tide) residents being exposed.
Highlights
The main objective of this study is to assess Alexandria, Egypt, in terms of damage due to tsunami inundation, as well as the number of affected population
Alexandria is a major city in the Mediterranean Sea, developing along a narrow strip of coast about 70 km long, separating the Mediterranean Sea from the inland Lake Maryut that has an area of 75 km2
8.0 8.0 location, (2) simulation of the tsunamis and computation of the desired metrics in the target place and (3) computation of the local aggregate scenario by combining all the individual scenarios. This method can be called the method of the probable maximum tsunami (PMT) or equivalently, the worst-case credible tsunami (WCT) method
Summary
The main objective of this study is to assess Alexandria, Egypt, in terms of damage due to tsunami inundation, as well as the number of affected population. From a physiographic point of view, the city of Alexandria lies on a series of narrow Late Pleistocene ridges running parallel to the coast separating the sea from the very shallow Lake Maryut, which is one of the many lagoons and marshes characterizing the vast area of the Nile Delta These brackish lakes are connected to the sea by a complex system of artificial waterways, two of which, the Alexandria and the Al-Max channels, drain the waters of the Lake Maryut into the Alexandria harbour basin by means of pumping stations, between the port of Dekhila and the western port of Alexandria in the district of Wassat. We will only recall their most relevant features in the following
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