Abstract
BackgroundThe Atlantic Coast of Morocco is prone to tsunami inundation. Therefore, in this region, earthquake-induced tsunami hazard has been intensively investigated leading to the development of a number of coastal inundation models. However, tsunami vulnerability remains not well understood to the same extent as the hazard. In this study, we use high-resolution numerical modeling, detailed field survey and GIS-based multi-criteria analysis to assess the building tsunami vulnerability and its sensitivity to the tide variations. Asilah located in the northwestern Atlantic coast of Morocco, where the impact from the 1755 tsunami is well documented, constitutes the area of this study.ResultsTo model the source-to-coast tsunami processes we used the COMCOT (Cornell Multi-grid Coupled Tsunami Model) numerical code on a set of bathymetric/topographic grid layers (640 m, 160 m, 40 m and 10 m resolutions) with an initial sea-surface perturbation generated using Okada’s formulae and assuming an instantaneous seabed displacement. The tsunami source models in this study correspond to four 1755-like earthquake scenarios. Results show that Asilah’s built environment is highly vulnerable to the tsunami impact that can range from 1.99 to 2.46 km2 of inundation area, depending on the source and the tidal level considered. The level of building vulnerability decreases considerably when moving away from Asilah’s coastline. Moreover, the variation in the tidal level introduces large change in the modeled tsunami impact and, therefore, affects the level of building vulnerability. ConclusionThus, we suggest considering the effect of the tide when simulating tsunami hazard and vulnerability, particularly, in coasts where tidal variations are significant. This study provides hazard and vulnerability maps that can be useful to develop the tsunami awareness of the Moroccan coastal population.
Highlights
The Atlantic Coast of Morocco is prone to tsunami inundation
These analyses demonstrated that the northwest tip of the Atlantic coast of Morocco is prone to tsunami impact from the earthquake sources located in the South West Iberian Margin (SWIM) region (Blanc 2008; Blanc 2009; Kaabouben et al 2009)
Tsunami inundation A total of 12 simulations were run considering four earthquake scenarios and three tide conditions (MLLW, mean sea level (MSL) and mean higher high water (MHHW))
Summary
The Atlantic Coast of Morocco is prone to tsunami inundation. in this region, earthquakeinduced tsunami hazard has been intensively investigated leading to the development of a number of coastal inundation models. Asilah located in the northwestern Atlantic coast of Morocco, where the impact from the 1755 tsunami is well documented, constitutes the area of this study. A detailed analysis of historical collections and archives of the 1755 tsunami has been achieved by numerous researchers (Blanc 2008; Baptista and Miranda 2009; Blanc 2009; Kaabouben et al 2009) These analyses demonstrated that the northwest tip of the Atlantic coast of Morocco is prone to tsunami impact from the earthquake sources located in the SWIM region (Blanc 2008; Blanc 2009; Kaabouben et al 2009). The historical records mention an extreme impact of the 1755 tsunami on the city of Asilah, with waves surging the fortifications, which suggest a run-up of at least 15 m. Omira et al (2012), using tsunami numerical simulations, show that at some locations along the coast of Morocco the historical reports may overestimated the tsunami impact
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