Tsunamis can be deadly, but they needn’t be. Early warning and early action are effective tools to protect people, saving lives, and preventing the hazard from becoming a disaster. To be effective, tsunami early-warning systems must cover every at-risk person, they must be multi-hazard, and communities must be prepared so they can act quickly.
In December 2015, the UN General Assembly designated 5 November as World Tsunami Awareness Day, calling on countries, international bodies and civil society to raise tsunami awareness and share innovative approaches to risk reduction.
World Tsunami Awareness Day was the brainchild of Japan, which due to its repeated, bitter experience has over the years built up major expertise in areas such as tsunami early warning, public action and building back better after a disaster to reduce future impacts. UN Disaster Risk Reduction (UNDRR) facilitates the observance of World Tsunami Awareness Day in collaboration with the rest of the United Nations system.
Background
Tsunamis are rare events but can be extremely deadly. In the past 100 years, 58 of them have claimed more than 260,000 lives, or an average of 4,600 per disaster, surpassing any other natural hazard. The highest number of deaths in that period was in the Indian Ocean tsunami of December 2004. It caused an estimated 227,000 fatalities in 14 countries, with Indonesia, Sri Lanka, India and Thailand hardest-hit.
Just three weeks after that the international community came together in Kobe, in Japan’s Hyogo region. Governments adopted the 10-year Hyogo Framework for Action, the first comprehensive global agreement on disaster risk reduction.
They also created the Indian Ocean Tsunami Warning and Mitigation System, which boasts scores of seismographic and sea-level monitoring stations and disseminates alerts to national tsunami information centres.
Rapid urbanization and growing tourism in tsunami-prone regions are putting ever-more people in harm’s way. That makes the reduction of risk a key factor if the world is to achieve substantial reductions in disaster mortality – a primary goal of the Sendai Framework for Disaster Risk Reduction 2015-2030, the 15-year international agreement adopted in March 2015 to succeed the Hyogo Framework.
What are tsunamis?
The word "tsunami" comprises the Japanese words "tsu" (meaning harbour) and "nami" (meaning wave). A tsunami is a series of enormous waves created by an underwater disturbance usually associated with earthquakes occurring below or near the ocean.
Volcanic eruptions, submarine landslides, and coastal rock falls can also generate a tsunami, as can a large asteroid impacting the ocean. They originate from a vertical movement of the sea floor with the consequent displacement of water mass.
Tsunami waves often look like walls of water and can attack the shoreline and be dangerous for hours, with waves coming every 5 to 60 minutes.
The first wave may not be the largest, and often it is the 2nd, 3rd, 4th or even later waves that are the biggest. After one wave inundates, or floods inland, it recedes seaward often as far as a person can see, so the seafloor is exposed. The next wave then rushes ashore within minutes and carries with it many floating debris that were destroyed by previous waves.
