Articles | Volume 15, issue 12
Research article
17 Dec 2015
Research article |  | 17 Dec 2015

Scenario-based assessment of buildings' damage and population exposure due to earthquake-induced tsunamis for the town of Alexandria, Egypt

G. Pagnoni, A. Armigliato, and S. Tinti

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.

Short summary
We estimate the vulnerability of buildings and population exposure to tsunamis for the city of Alexandria, Egypt. The study is based on the worst-case tsunami scenario technique and focusses only on tsunamis induced by earthquakes. The results show that a 15km2 area can be inundated to the south-west of the port of Dekhila. More than 165 000 residents could be exposed and over 13400 buildings could be affected, hundreds of which could sustain damage, ranging from light damage to total collapse.
Final-revised paper