In the Mediterranean Sea, the probability that a large earthquake-triggered tsunami will occur in the coming decades is high. This paper identifies the submarine rupture of the Amorgos earthquake of July 9, 1956, which triggered the largest Mediterranean tsunami in the past two centuries. Using submarines, a large surface rupture along the 75-km long Amorgos fault was discovered, with a 9.8–16.8-m seafloor offset, compatible with a Mw7.5 event. This finding challenges the previous attribution of the largest tsunami wave to submarine mass-wasting and demonstrates that tsunami sources can be determined decades after an event, crucial for assessing future seismic and tsunami hazards.

Frédérique Leclerc, Sylvain Palagonia, Nathalie Feuillet, Paraskevi Nomikou, Danai Lampridou, Paul Barrière, Alexandre Dano, Eduardo Ochoa, Nuno Gracias, Javier Escartín