Impact of a 1755-like tsunami in Huelva, Spain

Abstract

Abstract. Coastal areas are highly exposed to natural hazards associated with the sea. In all cases where there is historical evidence for devastating tsunamis, as is the case of the southern coasts of the Iberian Peninsula, there is a need for quantitative hazard tsunami assessment to support spatial planning. Also, local authorities must be able to act towards the population protection in a preemptive way, to inform "what to do" and "where to go" and in an alarm, to make people aware of the incoming danger. With this in mind, we investigated the inundation extent, run-up and water depths, of a 1755-like event on the region of Huelva, located on the Spanish southwestern coast, one of the regions that was affected in the past by several high energy events, as proved by historical documents and sedimentological data. Modelling was made with a slightly modified version of the COMCOT (Cornell Multi-grid Coupled Tsunami Model) code. Sensitivity tests were performed for a single source in order to understand the relevance and influence of the source parameters in the inundation extent and the fundamental impact parameters. We show that a 1755-like event will have a dramatic impact in a large area close to Huelva inundating an area between 82 and 92 km 2 and reaching maximum run-up around 5 m. In this sense our results show that small variations on the characteristics of the tsunami source are not too significant for the impact assessment. We show that the maximum flow depth and the maximum run-up increase with the average slip on the source, while the strike of the fault is not a critical factor as Huelva is significantly far away from the potential sources identified up to now. We also show that the maximum flow depth within the inundated area is very dependent on the tidal level, while maximum run-up is less affected, as a consequence of the complex morphology of the area.Correspondence to:

Potential inundation of Lisbon downtown by a 1755-like tsunami

“…A TIN (Triangular Irregular Network) with all these data points, including the zero height line as constraints and break-lines representing surface discontinuities close to the shoreline (harbor, pier, quay), was constructed. The procedures were similar to those described in Lima et al (2010), where the accuracy of the grid was evaluated as better than 0.5 m inland. Offshore the swath bathymetry data has an accuracy depth dependent which can be considered as compatible with on-shore data.…”

“…Previous tsunami simulations by Baptista et al (2003) and Gutscher et al (2006) and recent inundation studies in the area used these scenarios (see Omira et al, 2010;Lima et al, 2010) have showed the individual properties of such tsunami sources: the GF fault, located north of the Gorringe bank, radiates most energy towards North America and Morocco; the PB fault being almost parallel to the South Portuguese coast is not effective in producing a devastating tsunami along the west coast of Portugal, where Lisbon is located. The CW is the biggest structure identified in the area which is very effective in radiating energy towards the Strait of Gibraltar, but it seems unable to explain the tsunami observed on the west coast.…”

Approaches for tsunami risk assessment and application to the city of Cádiz, Spain

“…This area of tectonic deformation is responsible for the offshore seismicity of south-western Iberia. The worst cases, as well as the fault traces that we used for the Cadiz Bay area, are described in Lima et al (2010), and their summary is presented in Table 3, A more detailed description of the tSllllami sources is provided in DC-IGN (2009) and DCA (2009). The tSllllami risk was only estimated for the population distributed in 112 municipal districts of Cadiz.…”

Performance of coastal sea-defense infrastructure at El Jadida (Morocco) against tsunami threat: lessons learned from the Japanese 11 March 2011 tsunami

“…The tsunami hazard in the Gulf of Cadiz region, which is an important component of a TWS, is well established through the elaboration of the historical tsunami catalogs Kaabouben et al, 2009;Blanc, 2009), the definition of the tsunamigenic scenarios (Omira et al, 2009), the identification of tsunami deposits (Ruiz et al, 2005;Font et al, 2010;Medina et al, 2011;Costa et al, 2011), and the estimations of the waves' impact Lima et al, 2010;Baptista et al, 2011a). Moreover, major efforts have been addressed to enhance the seismic network to cover areas around the Azores-Gibraltar plate boundary, and in particular the Cadiz Gulf region.…”

“…In the Gulf of Cadiz coastal areas, various studies have been addressed to investigate tsunami impact (Lima et al, 2010;Omira et al, 2011;Baptista et al, 2011a), and the area's vulnerability . These works and this paper show the high level of destruction that coastal areas of Morocco, Portugal and Spain could experience following the occurrence of large regional tsunami events, and hence the need for robust TWS in the region to mitigate the tsunami hazard.…”