This scientific article explains the methodology followed by a group of researchers for the modelling of big sources of earthquakes and tsunamis, following some historical compilation of data concerning the tsunami generated by the earthquake of 11th January 1755 which affected mainly the coast of the Iberian Peninsula and Northwest Morocco, but also all over the North Atlantic coasts. This event caused at least 10000 casualties in Lisbon alone. The overall objective of the study was to assure significant improvement of tsunami hazard and risk assessments, as well as the methodology to set up early warning systems. (UNEsCO)