TSUNAMI 16th ANNIVERSARY

Subject : Environment

Context : December 26, 2020 marks the 16th anniversary of the Indian Ocean Tsunami.

Concept :

Tsunami is a Japanese word for “Harbour wave”. A tsunami is a series of very long-wavelength waves in large water bodies like seas or large lakes caused by a major disturbance above or below the water surface or due to the displacement of a large volume of water.
They are sometimes referred to as tidal waves because of long wavelengths, although the attractions of the Moon and Sun play no role in their formation.
Earthquakes (e.g. 2004 Indian Ocean Tsunami), volcanic eruptions (e.g. tsunami caused by the violent eruption of Krakatoa in 1883), landslides (tsunami caused by the collapse of a section of Anak Krakatoa in 2018), underwater explosions, meteorite impacts, etc. have the potential to generate a tsunami.

Mechanism of Tsunami Waves

Megathrust earthquakes cause a sudden displacement in a seabed sufficient to cause the sudden raising of a large body of water.
As the subducting plate plunges beneath the less dense plate, stresses build-up, the locked zone between the plates give way abruptly, and the parts of the oceanic crust is then upthrust resulting in the displacement of a large column of water vertically.
The tsunami on December 26, 2004, was caused after an earthquake displaced the seabed off the coast of Sumatra, Indonesia.
A marine volcanic eruption can generate an impulsive force that displaces the water column and gives birth to a tsunami.
During a submarine landslide, the equilibrium sea-level is altered by sediment moving along the floor of the sea. Gravitational forces then propagate a tsunami.
Most destructive tsunamis can be caused due to the fall of extra-terrestrial objects on to the earth.

2004 Indian Ocean Tsunami

The earthquake of 9.2 magnitude occurred in Indian Ocean near the Sumatra-Andaman Subduction Zone.
This triggered a massive and largest Tsunami in the Indian Ocean region. Over 2.3 lakh people died across 14 countries in the Indian Ocean region and out of which the major affected countries were Indonesia, Thailand, Sri Lanka and India.
At that time there was no Tsunami warning system in place in India. Though similar system existed in other parts of the world in pacific and Atlantic, but was not able to provide early warning to the Indian Ocean region.

Tsunami Early Warning System

Within 2 years a state-of-the-art Tsunami warning system was established at Indian National Centre for Ocean Information Services (INCOIS), Hyderabad.
By October 2007, 24*7 early warning systems was in place which is capable of giving early warning within 10 minutes of occurrence of earthquake anywhere in Indian Ocean region.
INCOIS is developing 3D GIS mapping in vulnerable coastal areas to have new early warning systems for tsunamis in the eastern coast of India. This will be extended to other vulnerable areas of the Indian coasts.
There is a standard operating procedure to deal with Tsunami activities which are established by Tsunami warning centre at Hyderabad.
This information is passed on to National Disaster Management Authority within 10 minutes of occurrence of earthquake.
The coastal states administrators have been trained to provide the help required for the people living in the coastal region. There are periodic awareness programmes in the coastal region and people will be taught what to do when the Tsunami occurs.
In 2010 there was National Disaster Management Guidelines which emphasised on advanced systems like Topography, GIS database and remote sensing data.
Tsunami warning system is a system of systems where it requires various branches of science and technology to develop the system and make it operational. We require data from satellites, ocean observation systems, ships, and good communication to generate tsunami forecast.