Should we fear a Mediterranean Fukushima?

Although less frequent than those in the Pacific or Indian oceans, tsunamis in the Mediterranean Sea have caused extensive damage and loss of life. This is due to the significant frequency of tsunami events – according to the European Environment Agency 200 tsunamis were recorded over the last 500 years around the Mediterranean and the University of Bologna indicated that on average, in the last four centuries Italy has seen 15 tsunamis every 100 years - to the considerable population density along the Mediterranean coasts - around 150 million people concentrated on the 46,000 kms of coastline, with 110 million of them living in cities and some 200 million tourists arriving every year - and to the limited consideration of the tsunami risk in land use planning policies.

Tsunamis can be triggered by three types of geologic events causing the displacement of significant volumes of water: earthquakes, large landslides and volcanic activities.

Submarine earthquakes can abruptly deform the sea floor displacing huge quantities of water. Earthquakes can also trigger the destabilisation of large amounts of sediments deposited on coastal or submarine slopes causing giant landslides which displace large amounts of water and generate a tsunami. These landslides may take place right after the earthquake or may be delayed for days, weeks, or months.

Tsunamis are characterized by large wavelengths and velocities of approximately 700km/h in deep waters where they generate small waves (0.3 meters) and therefore are very difficult to detect. The wavelength causes a slowing down of these waves in shallower waters to around 100km/h. When tsunamis reach the shoreline they build up wave heights up to 30m and more.

In the Mediterranean, due to short travel times and thus very short early warning possibilities tsunami waves can cause severe damages. Most of the reported Mediterranean tsunamis occurred in the most seismic and volcanically active regions like the Aegean, Ionian and Tyrrhenian Seas, the Sea of Marmara and subsequently along the Algerian margin and Cyprus arc, or off-delta areas.

It is impossible to forecast tsunamis; it is only possible to outline potential impact areas associated with geologically active - earthquake and volcano - zones. However not every earthquake, volcanic eruption or submarine landslides necessarily trigger tsunamis.

To identify which Mediterranean coastal zones are particularly exposed to tsunami hazards, PPRD South collected and reviewed the results of various researches, scientific studies, tsunami simulations and tsunami risk assessment in the Mediterranean. Then, on the basis of existing risk maps and studies, the Programme tried to estimate the risks of nuclear or chemical accidents triggered by a tsunami. Finally, PPRD South outlined the existing legal provisions and recommendations for preventing tsunami-chemical accident domino effects in the Mediterranean.