Earthquakes, which are sometimes the cause of violent tsunamis when their epicentre is at sea, and many volcanic eruptions have often claimed victims and caused considerable damage, and these phenomena are still very often unpredictable. The earthquake that struck Lisbon on 1st November 1755, whose epicentre was in the Atlantic, 200 km off the coast, left its mark on Portugal’s history. Followed by a violent tsunami, it almost totally destroyed the capital, whose centre was submerged by waves 5 to 15 metres high, and claimed 60,000 victims. Voltaire echoed this event in his Poème sur le désastre de Lisbonne (1756) and in Candide (1759), and drew philosophical lessons from it.
Japan’s magnitude 9 Tohoku earthquake off the Pacific coast in March 2011 was followed by a tsunami that devastated the region and was responsible for 90% of the 16,000 victims. Despite a warning, the tsunami triggered the Fukushima nuclear disaster, with the backup and security facilities of several nuclear power plant reactors and the electricity grid having been destroyed or damaged by the waves.
Little progress has been made in developing techniques for detecting an earthquake on the ocean floor and simultaneously sending a long-distance warning. Seismometers can be placed on the ocean floor but, as well as being expensive to install and requiring maintenance, they are fragile and cannot broadcast data in real time. Buoys called M
