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What is the definition of “Tsunami” ?

Tsunami is a Japanese word. Its literal meaning is the wave of the harbour. Here ‘tsu’ means port or harbour and ‘nami’ means sea waves. The tsunami originated at sea level. A tsunami is the huge wave that occurs at the sea level when a strong earthquake occurs at the bottom of the sea. The first tsunami was recorded in 1500 BC.

Causes of tsunami formation and tsunami movement “Geo-tectonics” at sea level :

The vibrations caused by the earth’s movement due to the process are mainly in two ways. Namely, during the tsunami in parallel and vertically, there is a stir in the sea floor. As a result, a place on the surface of the sea floor sits across a large area or a place rises steeply before and causes cracks in the sea floor, which in turn destroys the uniformity of the bottom. 

In order to quickly maintain the water level of the sea level, there is a tremendous sub-pressure of the water. As a result, a tsunami was created to protect the balance of surface water. The main cause of the tsunami is the earthquake at the bottom of the sea. Tsunamis are also caused by volcanic eruptions. In addition, a tsunami can also be caused by nuclear explosions, rolls, the collapse of the height, etc.

The waves caused by the earthquake on the seafloor move towards the coast at a great speed. Each wave of the tsunami flows at a speed of 640 km per hour. As the tsunami wave approaches the coast, the intensity of the wave speed decreases, but the height of the wave increases manifold. The height of the tsunami is only a few cm at the origin of the tsunami in the deep sea. High but the height of tsunami waves on the coast is 30-50 metres high.

Why do we celebrate World Tsunami Awareness Day ?

In December 2015, the UNGA (United Nations General Assembly) designated November 5 as World Tsunami Awareness Day to raise awareness and share innovative methods for risk reduction during tsunamis.

Tsunami Warnings:

Warning messages and signals about a possible tsunami can come from several sources – natural, official or unofficial.

Natural warnings: For a local source tsunami which could arrive in minutes, there won’t be time for an official warning. It is important to recognise the natural warning signs and act quickly.

Unofficial or informal warnings: You may receive warnings from friends, other members of the public, international media and from the internet. Verify the warning only if you can do so quickly. If official warnings are available, trust their message over informal warnings.

Official warnings: Official warnings are only possible for distant and regional source tsunamis. Official warnings are disseminated by the Ministry of Civil Defence & Emergency Management to the national media, local authorities and other key response agencies. Your local council may also issue warnings through local media, siren and other local arrangements.

What are the 11 biggest tsunamis ?

1. Tōhoku earthquake and tsunami 11 March 2011
2. Indian Ocean earthquake and tsunami 26 December 2004
3. The Alaska Tsunami March 27, 1964
4. Sanriku, Japan – 15 June 1896
5. Krakatau, Indonesia – 27 August 1883
6. Northern Chile – 13 August 1868
7. Ryukyu Islands, Japan – 24 April 1771
8. Lisbon, Portugal – 1 November 1755
9. Nankaido, Japan – 28 October 1707
10. Ise Bay, Japan – 18 January 1586
11. Enshunada Sea, Japan – 20 September 1498

Tsunamis Background:

By the year 2030, an estimated 50 percent of the world’s population will live in coastal areas exposed to flooding, storms, and tsunamis (UNESCO-IOC, 2021). Scaling up regional support to developing countries will help ensure that 100% of communities at risk of tsunami are prepared for and resilient to tsunamis by 2030. The trillions of dollars that are needed to achieve the Sustainable Development Goals – particularly in these contexts – must be invested in a risk-informed and resilient manner lest these investments end up as disaster risk and losses.

The Asia and Pacific is one of the most tsunami-affected regions in the world. The January 2022 Tonga tsunami event, triggered by a Hunga Tonga- Hunga Ha’apai submarine volcanic eruption, demonstrated the multi-hazard nature of risks and how their impacts can cascade through multiple chains affecting directly exposed communities and their livelihoods. 

It also triggered national and global disruptions in the telecommunication system as a critical cluster of submarine fibre-optic cable was affected. The telecommunication outage experienced in Tonga compounded the challenges faced by affected communities, hampering the coordination of relief efforts, and making it close to impossible to send vital updates. The memory of tsunamis with large death tolls like the 2004 Indian Ocean earthquake and tsunami is still vivid among those impacted communities. Affected countries like Indonesia, Thailand, Japan and the Maldives often cultivate a culture of memory and learning from past experiences.

World Tsunami Awareness Day History: 

On December 22, 2015, the United Nations, through resolution 70/23, designated November 5 as World Tsunami Awareness Day. Although they are rare, tsunamis are one of the most devastating and dangerous natural disasters. They have no borders since they do not affect only coastal communities. They also reach and destroy other towns and communities that are located away from the coast.

Coastal communities are the most vulnerable when there is a risk of a tsunami. Even though tsunamis are hazardous, there are often natural warnings that a tsunami may be approaching. It could be strong ground shaking, volcanic eruptions, or the water receding unusually far and exposing the seafloor. International cooperation is key in trying to raise global awareness about effective actions, policies, and practices to reduce exposure to this kind of natural disaster.

About 58 tsunamis have taken more than 260,000 lives in the past 100 years, more than any other natural disaster. The highest number of deaths during those 100 years occurred in December 2004 when the Indian Ocean tsunami took place. It caused approximately 227,000 fatalities in 14 countries, including Indonesia, Sri Lanka, India, and Thailand. Just three weeks after that tsunami, the international community came together in Kobe, Japan, where Governments adopted the 10-year Hyogo Framework for Action. This agreement was the first comprehensive global agreement on disaster risk reduction.

Rapid urbanisation and growing tourism in tsunami regions are putting even more people in danger. That is why it is so important that the world makes everything possible to achieve a substantial reduction in disaster mortality.