Context: Recently, the Indian Tsunami Early Warning Centre (ITEWC), part of the Indian National Centre for Ocean Information Services (INCOIS) in Hyderabad, confirmed that India faces no tsunami threat despite a 7.5 magnitude earthquake near Honshu, Japan.

What is a Tsunami?

• Tsunami (a Japanese word that means “harbor wave”) is a series of giant ocean waves caused by earthquakes or volcanic eruptions under the ocean. 

• The formation of a tsunami can depend on a host of factors, including the shape of the ocean floor, and the earthquake’s distance and direction.

• The speed of a tsunami depends on the depth of the water it is traveling through. The deeper the water; the faster the tsunami. 

Causes of Tsunami

• Earthquake: When an earthquake takes place under the ocean, a large chunk of the ocean floor can suddenly move upward or downward, leading to a sudden displacement of a large volume of water, thereby causing tsunami waves.

• Volcano eruption: When a volcano erupts in the ocean, the lava flowing out of the volcano displaces the water around it and that water can become a large wave.

How are tsunamis detected?

• Seismic Networks: When an earthquake occurs, seismic networks provide information about an earthquake’s location, depth, magnitude, and other source characteristics.

• The warning centers analyze this information to determine if the earthquake could have generated a tsunami and if a tsunami message is necessary.

• Water-Level Networks: If an earthquake meets certain criteria, the warning centers turn to water-level information, looking for changes in water-level height that could indicate the existence and size of a tsunami.

• The primary sources of information about water-level change are a network of Deep-ocean Assessment and Reporting of Tsunami (DART) systems and an extensive array of coastal water-level stations.

Consequences of Tsunami

• Loss of Life: Tsunamis can cause significant loss of life, especially in densely populated coastal regions.

• In 2011, Japan was hit by a 9.0 magnitude earthquake and a resulting tsunami which  killed around 18,000 people

• Major Accidents: The 2011 tsunami in Japan led to a nuclear meltdown at the Fukushima power plant, causing one of the most severe nuclear accidents.

• Displacement of Communities: People living in coastal areas are forced to evacuate or relocate which can lead to temporary or long-term homelessness and strain on resources.

• Infrastructure Disruption: Tsunamis can damage critical infrastructure such as roads, bridges, ports, and utilities, disrupting transportation and communication networks. 

Why is Japan prone to earthquakes and tsunamis?

• Japan is situated along the ‘Pacific Ring of Fire’, which is the most active earthquake tectonic belt in the world. 

• The ‘ring’ refers to “an imaginary horseshoe-shaped zone that follows the rim of the Pacific Ocean, where many of the world’s earthquakes and volcanic eruptions occur,”

• Within the Ring of Fire, there are different tectonic belts, including the Pacific Plate, Eurasian Plate, and Indo-Australian Plate, which keep meshing and colliding with each other, causing earthquakes, volcanic eruptions and tsunamis.

Indian National Centre for Ocean Information Services (INCOIS)

• INCOIS is an autonomous body under the Ministry of Earth Sciences (MoES) and is a unit of the Earth System Science Organisation (ESSO).

• ESSO-INCOIS was established in 1999 under the Ministry of Earth Sciences (MoES) and is located in Hyderabad.

• Indian Tsunami Early Warning Centre (ITEWC) is also housed in the INCOIS.

• Mandate: To provide the ocean information and advisory services to society, industry, government agencies and scientific community through sustained ocean observations and systematic and focussed research.