Alcuni momenti della campagna di deposizione delle boe di mare profondo nel Mare Ionio An important step forward in mitigating tsunami risk on our coasts has been taken by the deposition of two deep-sea buoys in the Ionian Sea that detect the arrival of tsunami in real time. These are the first buoys for monitoring tsunamis in the Mediterranean Sea. The deployment campaign took place from September 9 to 17, 2025, organized by the Tsunami Alert Centre (CAT) of the National Institute of Geophysics and Volcanology (INGV), as part of the MEET Project “Monitoring Earth's Evolution and Tectonics” funded by the PNRR.
The deployment was carried out aboard the ship Christos LVII, which departed from Sagunto, Spain, and involved three INGV technicians (Antonio Costanza, Andrea Di Benedetto, and Francesco Macaluso), as well as the ship's crew and Mediterráneo Señales Marítimas (MSM), the Spanish company that manufactured the buoys. In this in-depth article, we explain the importance of the mission and how the buoys work.
Why monitor the Mediterranean Sea?
The Mediterranean Sea is a semi-enclosed sea that communicates with the Atlantic Ocean through the Strait of Gibraltar and with the Indian Ocean through the Suez Canal. The basin is nestled between the coasts of southern Europe, northern Africa, and Asia Minor. Its current shape is the result of a long geological evolution linked to the convergence of the African and Arabian plates with the Eurasian plate, complicated by the presence of several crustal blocks or microplates, such as the Adriatic plate. The deformation of the margins of these blocks manifests itself in earthquakes, most of which occur at sea or near the coasts. The strongest of these have the potential to generate tsunamis.
Throughout its history, the Mare Nostrum has been affected by major tsunamis, some of which have caused loss of life and extensive damage along the coasts. The Ionian Sea, in particular, is one of the most critical areas due to the presence of major active faults located along the Hellenic arc, the Ionian islands, and near the Italian coast. Some of these faults have characteristics that make them potential sources of tsunamis.
The EMTC Euro-Mediterranean Tsunami Catalogue lists approximately 220 tsunamis in the Mediterranean from 1600 BC to the present day, as reconstructed in the Storymaps ‘Travelling through the tsunamis of the Mediterranean Sea’. Almost 90% of the tsunåamis listed in the catalog are of seismic origin, while others were generated by other types of sources, such as underwater landslides, or linked to volcanic activity. Among the most significant events, we recall the tsunami of 365 AD in Crete, or that of 1908 generated by the earthquake in the Strait of Messina, or, more recently, the one that occurred following the landslides on Stromboli in 2002.
Today, it is estimated that between 10 and 12% of the total European population, approximately 180 million people, live along the Mediterranean coast (within 50 km of the sea). In Italy, coastal municipalities—defined as those with at least 50% of their surface area within 10 km of the sea—are home to over 20 million inhabitants, a number that grows significantly during the summer season thanks to the influx of tourists. In the event of a tsunami, coastal communities could be hit by the tsunami in a time estimated to vary between a few seconds and 30-40 minutes, depending on the location of the event's origin. Nevertheless, recent surveys show that the tsunami risk perception among those living in coastal areas – and among the Italian population in general – is low. This is why non-structural prevention measures are important in order to raise awareness among citizens, such as the national campaign Io non rischio (I don't take risks), and why it is essential for the authorities responsible for monitoring to improve the warning system with rapid and effective tools.
The warning system
The Italian National Warning System for Seismic Tsunamis (SiAM) has been active since 2017. It is coordinated by the Department of Civil Protection (DPC) and consists of the INGV Tsunami Alert Centre and the Higher Institute for Environmental Protection and Research (ISPRA). The CAT, in particular, acts as a Tsunami Service Provider (TSP) for the Euro-Mediterranean area, providing alerts to numerous European, African, and Asian countries bordering the Mediterranean, as well as to the DPC. The CAT manages the alert chain in the so-called Upstream phase, which includes monitoring seismic phenomena and transmitting alerts to the Department of Civil Protection, which in turn is responsible for disseminating the alert. The system uses a network of sensors that record seismic waves and tide gauges that detect changes in sea level. The Italian Tide Gauge Network, managed by ISPRA, currently consists of 41 tide gauges located in various Italian ports. Tsunami monitoring initially involves analyzing earthquake parameters such as magnitude, depth, and distance from the coast, followed by analysis of tide gauge signals. However, a system based solely on these instruments can only confirm the generation of a tsunami once it has already reached the coast.
More effective monitoring with faster instruments
To improve the system and make it faster and more effective, a group of INGV researchers and technologists has been studying tsunamis and marine monitoring techniques for some time. This process includes the design, construction, and deployment of the first two deep-sea buoys off the Ionian Sea. The first was positioned about 100 km east of the eastern coast of Sicily at a depth of approximately 3200 m, while the second was positioned about 100 km east of Calabria at a depth of approximately 2600 m. Both buoys are located about 100 km from the coast and have been positioned at strategic points, identified following a study that takes into account the tsunami hazard associated within the area, numerical modeling of approximately 200k tsunami scenarios, and the time between the occurrence of a hypothetical seismic event and its observation at a point of the tsunami that may be generated.
Let's see how they work. Each of the two buoys, anchored to the seabed, has been connected to two sensors that measure the pressure exerted by the water column above and can be placed thousands of meters below sea level, as in our case. The buoys receive data from the sensors via an acoustic link and transmit it via satellite to the INGV Tsunami Alert Centre. The absolute pressure sensors are capable of detecting variations in the height of the water column above them of a few centimeters, enabling them to distinguish between waves caused by wind, tides, and possible tsunami waves. In the event of a tsunami, the pressure sensors begin to transmit data at a higher frequency to allow accurate measurement of the tsunami waves, assisting real-time forecasting and reducing the time needed to confirm the imminent arrival of a tsunami on our coasts or to cancel the alert. Before being integrated into the INGV Tsunami Alert Centre's monitoring system, the data will be subjected to a preliminary testing as well as verification phase, aimed at ensuring its reliability.