Marseille, Alexandria and Istanbul are preparing for the Mediterranean tsunami

Marseille, Alexandria and Istanbul are preparing for the Mediterranean tsunami

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A tsunami could soon hit major cities on or near the Mediterranean Sea, including Marseille, Alexandria and Istanbul, with a nearly 100 percent chance of a wave exceeding a meter in height over the next 30 years, Unesco says.

The risk of a tsunami in Mediterranean coastal communities is expected to increase as sea levels rise. While communities in the Pacific and Indian Oceans, where most tsunamis occur, were often aware of the dangers, in other coastal regions, including the Mediterranean, it was underestimated, Unesco said.

Now the United Nations Educational, Scientific and Cultural Organization said five vulnerable communities in the Mediterranean will join 40 other “tsunami-ready” cities in 21 countries by next year. In addition to Marseille, Alexandria and Istanbul, these also include Cannes and Chipiona, a city on the Spanish Atlantic coast near Cádiz.

A huge wave piles up over the coastal road, taking cars with it

The moment the tsunami hit the Miyako coast from the Heigawa Estuary after a massive 9.1 magnitude earthquake struck Japan in 2011. Photo: Mainichi Shimbun/Reuters

The Tsunami Ready program is part of Unesco’s broader effort, launched ahead of the UN Oceans Conference in Lisbon next week, to ensure all vulnerable communities know what to do in the event of a tsunami by 2030.

“The 2004 and 2011 tsunamis were a wake-up call,” said Bernardo Aliaga, UNESCO’s chief tsunami expert. “We have come a long way since 2004. Today we are safer. But there are gaps in the preparation and we need to improve; We need to make sure visitors and communities understand the warnings.”

The 2004 Boxing Day Indian Ocean tsunami, the deadliest in history, killed an estimated 230,000 people in 14 countries, while the 2011 magnitude 9.1 earthquake and tsunami, which hit nearly 40 meters (130 feet) reached, 18,000 people killed Japan.

Since the 2004 Indian Ocean tsunami, Unesco’s US-run Pacific Tsunami Warning Center has responded to 125 tsunami events, an average of seven per year.

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“The upstream portion is in good condition,” Aliaga said. “Work has been underway to set up 12 tsunami warning centers covering most of the ocean, including the Mediterranean Sea.”

The alert centers include five in the Mediterranean and the north-east Atlantic, including Greece, Turkey, Italy, France and Portugal.

“The tsunami risk is underestimated in most areas, including the Mediterranean Sea,” Aliaga said. “Events are not very frequent and the risk is not transmitted from one generation to the next.

“We have to spread the message,” he added. “In the Mediterranean, it’s not a question: it’s not if, it’s when.”

One of the deadliest earthquakes in history struck Portugal on All Saints’ Day 1755, triggering a 6 meter high tsunami in Lisbon and Cádiz. Up to 50,000 people died in the earthquake, but many unwitting others died in the fires and tsunami that followed.

Engraving depicting the 1755 Lisbon earthquake.

An engraving depicting the 1755 Lisbon earthquake, fire and tsunami. Photo: Science History Images/Alamy

Tsunamis as small as 1.5 to 2 meters high can lift cars off the ground, while smaller waves can create walls of water moving at 40 mph.

“The warning isn’t the whole story,” Aliaga said. “The second part is community readiness – how people behave and react. That still has a long way to go.”

He cited the case of Tilly Smith, a 10-year-old British girl who rescued 100 people, including her family, in the 2004 tsunami. Her geography teacher at school had told her to evacuate as soon as she saw any receding water.

Rising sea levels, which amplifies the impact of tsunamis on coastal communities, is “another reason to increase the pace of our work,” he said.

“The connection is that sea-level rise amplifies the effects of tsunamis.”

A 2018 study modeling tsunamis in Macau, China found that rising sea levels increase the risk of tsunamis because they can travel further inland. The frequency of tsunami-induced flooding increased 1.2- to 2.4-fold for a 45 cm rise in sea level and 1.5- to 4.7-fold for a 90 cm rise, the researchers said Study.

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Authorities in Alexandria, Istanbul, Marseille, Cannes and Chipiona are working on “tsunami-ready” preparations, including evacuation signs and procedures and plans to warn tourists, Aliaga said.

“We want 100% of communities where there is a proven risk to be ready to respond by 2030,” he said. “They will have evacuation maps, they will have drills conducted and they will already have 24-hour alerts.”

Alerts would go off about 10 minutes after an earthquake, he said, and could take the form of everything from megaphones to WhatsApp messages.

“With a local tsunami, you have a maximum of 20 minutes before the first wave hits. The second wave is larger and arrives 40 minutes after the first. You still have a chance to escape.”

Vladimir Ryabinin, Executive Secretary of Unesco’s Intergovernmental Oceanographic Commission, said: “More than 40 communities in 21 countries are already safer after implementing our tsunami preparedness program. If we want to meet this global challenge by 2030, we need to scale up our program very quickly.”

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