Impact of a tsunami generated at the Lesser Antilles subduction zone on the Northern Atlantic Ocean coastlines

Abstract

Abstract. On 11 March 2011, a M w ∼ 9.0 megathrust earthquake occurred off the coast of Tohoku, triggering a catastrophic tsunami reaching heights of 10 m and more in some places and resulting in lots of casualties and destructions. It is one of a handful of catastrophic tsunamis having occurred during the last decade, following the 2004 Indonesian tsunami, and leading to the preparation of tsunami warning systems and evacuation plans all around the world. In the Atlantic Ocean, which has been struck by two certified transoceanic tsunamis over the past centuries (the 1755 "Lisbon" and 1929 Grand Banks events), a warning system is also under discussion, especially for what concerns potential tsunamigenic sources off Iberian Peninsula. In addition, the Lesser Antilles subduction zone is also potentially able to generate powerful megathrust ruptures as the 8 February 1843 M w ∼ 8.0/8.5 earthquake, that could trigger devastating tsunamis propagating across the Northern Atlantic Ocean. The question is in which conditions these tsunamis could be able to reach the Oceanic Islands as well as the eastern shores of the Atlantic Ocean, and what could be the estimated times to react and wave heights to expect? This paper attempts to answer those questions through the use of numerical modelings and recent research results about the Lesser Antilles ability to produce megathrust earthquakes.

Soliciting historical data to better understand disasters. The marine submersion of La Rochelle on 6 September 1785

“…Le risque de tsunami induit par un séisme lointain apparaît relativement faible dans la région rochelaise, compte tenu de l'effet protecteur des îles de Ré et d'Oléron. Des modélisations numériques reproduisant le séisme de Lisbonne en 1755 48 ou un séisme fictif localisé dans l'arc antillais 49 ne génèrent des surcotes de l'ordre que de quelques dizaines de centimètres au plus. L'important tsunami induit par l'explosion du Krakatoa le 28 août 1883, pourtant distante de plusieurs milliers de kilomètres, a été enregistré par le marégraphe de Rochefort mais n'a atteint qu'une amplitude de 20 cm environ 50 .…”