Tsunami hazard induced by a submarine landslide in the Tagus delta off Lisbon (Portugal)

I. Ramalho (), R. Omira and P. Terrinha
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I. Ramalho: Instituto Português do Mar e da Atmosfera, IPMA, I. P.
R. Omira: Instituto Português do Mar e da Atmosfera, IPMA, I. P.
P. Terrinha: Instituto Português do Mar e da Atmosfera, IPMA, I. P.

Natural Hazards: Journal of the International Society for the Prevention and Mitigation of Natural Hazards, 2025, vol. 121, issue 6, No 8, 6570 pages

Abstract: Abstract Submarine landslides can be a major source of tsunamis, with waves highly dependent of the properties of both the landslide and the marine domain. This study investigates the tsunamigenesis of a shallow-water submarine landslide, recently mapped at the mouth of the Tagus delta River, off Lisbon, Portugal. The Tagus delta landslide is estimated to be 8 ky old, with a depositional maximum thickness of ~ 20 m and a volume of approximately 0.27 km3, extending over more than 9 km in length and 3 km in width. We assess the tsunamigenic potential and hazard of this possible early Holocene landslide using numerical simulations over high resolution reconstructed paleo-bathymetry, and project a similar future landslide scenario under the present-day conditions. Results show that both paleo- and future landslide scenarios are tsunamigenic, posing a significant hazard to the nearest coasts of Lisbon and surrounding areas. At the source region, the modelled tsunami reached heights of 0.8 m (paleo-scenario) and 1.45 m (future-scenario), increasing to approximately 2 m (both scenarios) as it propagated towards Lisbon’s coastline. This study is a first attempt to address the tsunamigenic potential of a submarine landslide occurring in a shallow water environment of the Portuguese margin domain. The results reinforce the need to include these small, but frequent, events and their induced tsunamis in marine geo-hazard assessments of the region.

Keywords: Tsunami; Landslide; Hazard extent; Numerical modelling; Tagus delta; NE Atlantic (search for similar items in EconPapers)
Date: 2025
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DOI: 10.1007/s11069-024-07045-7

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