Indonesia, Thailand and Sri Lanka were the three countries that suffered the most extensive damage after the earthquake and subsequent tsunami of that tragic December 26th 20 years ago. But those anomalous waves up to 30 meters high hit the coasts of 14 countries in total, killing more than 220 thousand people, leaving millions of survivors homeless and shocking the whole world.
That tsunami – the deadliest natural disaster of the 21st century and one of the deadliest in history – became a “alarm bell” for early warning systems, as stated by the then head of UNESCO’s Tsunami Ready Programme, Bernado Aliaga. But would we really be better prepared today?
What seems clear is that over the past two decades, the legacy of this disaster has forever changed the face of tsunami science. But what has changed since then? Would we be better prepared today to face a tragedy of this magnitude?
What happened
Around 1 a.m. local time on December 26, a seismometer in Australia detected a massive 9.1 magnitude earthquake off the coast of Sumatra, Indonesia.
About 20 minutes later, a shocking tsunami reached the coast of the Indonesian province of Aceh. Waves up to 50 meters high inundated the region, traveling across the Indian Ocean at the speed of a jet plane.
More than 225 thousand people have been killed and two million left homeless due to flooding of coastal communities in Indonesia, Sri Lanka, India, Thailand and numerous other countries.
And what could happen
Around 700 million people worldwide live in areas vulnerable to ocean hazards, and this number is expected to reach one billion by 2050. While around 80% of tsunamis are generated by earthquakes, they can also be triggered by underwater landslides and volcanoes.
There is one area in particular that is most vulnerable to these disasters: Nearly 70% of all deadly tsunamis occur in the Pacific Ocean and 90% of deaths are caused by local or regional events that strike within a few hours. But they can strike anywhere there has been such an event before, including the Indian Ocean, parts of South America such as Chile and Peru, and even the Mediterranean.
The progress made in prevention
In 2004, data that helped inform potential disasters was limited. The tsunami risk was considered low in Indonesia, one of the most affected countries. There was little to no information on sea surface levels from the region and even Indonesian seismometers could only record earthquakes up to a magnitude of 6.5.
After the disaster, the international community invested heavily in the prevention and management of tsunami emergencies. One of the most significant achievements was the establishment of the Indian Ocean Tsunami Warning Systema joint initiative between governments, international organizations and research institutes. This system constantly monitors seismic activity in the region and sends timely alerts to local authorities in case of danger.
Awareness of coastal communities has also improved. Many countries have introduced education and awareness programmes, with periodic exercises to teach people how to recognize the signs of a possible tsunami and what to do to save themselves. Furthermore, more resilient infrastructure has been developed, such as natural barriers and more efficient evacuation systems.
But despite progress, significant challenges remain. Some areas, particularly those that are more remote or economically disadvantaged, still have a limited access to early warning systems. Furthermore, needless to say, climate change is amplifying the impact of extreme weather events and raising sea levels, increasing the risk for many coastal communities.
And not only that: another problem is the need for coordination between the various countries, which is not always obvious. In the event of a new tsunami, the speed and effectiveness of the response would depend on collaboration between the nations involved, a challenge that is not always easy to face.
Are there risks for Italy?
The twentieth anniversary of the tragic tsunami of 2004 is a time to reflect on what has been done and how much still remains to be done. Every breakthrough in technology, awareness and international cooperation represents hope for a future in which similar events can cause less suffering.
Even in Italy, many earthquakes and volcanic eruptions have occurred more or less recently, but it is rare that our coasts have also been affected by tsunamis (although it cannot be completely ruled out). The last disastrous tsunami was the one due to Messina earthquakeof 7.1 magnitude in 1908, which caused around 100 thousand victims between Sicily and Reggio Calabria.
Here is the geographical distribution of the events (earthquakes and volcanic eruptions) that gave rise to the tsunamis that occurred along the coasts of the Bel Paese, reworked by the INGV Tsunami Warning Centre:
