This day, on Dec 26, 2004, remains a dreaded occasion when an unprecedented sea-born disaster struck the chain of the Bay of Bengal Islands and South Peninsular India. An earthquake of a very great magnitude of 9.1 on the Richter scale struck south of the Nicobar Islands in the South Andaman Sea in the proximity of the Mentawai Islands of Indonesia, in the equatorial region of the Indian Ocean. The epicentre of the earthquake was 3.3°N and 95.8°E, deep in the ocean, triggering Tsunami impacting India, Indonesia and Myanmar. This, Sunday’s earthquake occurred when a 1200km stretch of the Indian plate which moves at a rate of 6cm/year towards the Myanmar plate slipped under the latter by about 15 meters. The result was ‘cataclysmic’. It caused a 100 km stretch of the plate edge to rupture. This, in turn, released huge amount of energy, causing displacement of extremely large volumes of water, triggering the killer tsunami.
Amongst all-natural disasters, an earthquake is feared the most. This is perhaps due to the fact that it follows no season and strikes with amazing suddenness. As compared to other severe natural disasters, such as floods and cyclones, the duration of an earthquake is very small, a few sore seconds. But the catastrophic potential is the largest, and more so, when erupts over the sea. The earth’s surface sits on gigantic tectonic plates that move a few centimetres every year. They often move against each other, causing huge stresses to build at the edges. Occasionally, the edges break under pressure, causing earthquakes. Four such gigantic plates are in uneasy equilibrium under the Sumatra region, making it a ‘hot spot’ for earthquakes.
The worst part of an earthquake is that it comes without warning, allowing no escape and traps the masses even hundreds of kilometres away from the epicentre. Anything happening in the dark hours adds to the degree of difficulty in assessing and planning a rescue. This ruinous tragedy of 2004 left 2,30,000 dead, about two million displaced/ homeless and around 50,000 bodies missing or untraced.
There was no tsunami early warning issued for the tragic event on 26th Dec 2004. Truly speaking, there was no effective system in place and the sea-born cataclysmic events could strike with no prior notice. This remains a grey area, even today. But, efforts are being made to have technology upgradation to build up efficacy and speed of information of tsunami events. Following the 2004 tsunami, under the leadership of UNESCO, the tsunami warning system in the Indian Ocean has been active since 2006. It consists of 25 seismographic stations, relaying information to 26 national tsunami information centres as well as six Deep-ocean Assessment and Reporting of Tsunami ( DART) buoys. Indonesia is developing a new offshore tsunami early warning system using GPS to monitor sea level changes, a precursor to the tsunami occurrence. This could be implemented in the next 5 years.
Some signs of a tsunami include: a large earthquake or a long weak rolling earthquake that lasts a minute or more, sudden drop in sea level, exposing reef, rocks and fish on the sea bottom and a loud roar like an incoming train or jet aircraft. Dissemination systems include radio and wireless technology and the local radio and television.
The capability at hand to predict tsunamis is far from the desired level. The sea-born platforms are neither sufficient in number nor suffice the efficacy. Amongst, all the warning systems include the most primitive one of issuing a tsunami warning, as an when a strong earthquake gets triggered deep in the ocean. In case, things remain quiet for the subsequent 6-8 hours, the warning is withdrawn from the respective coastal belt. A robust warning system, under the umbrella of World Weather Agency, still remains on the wish list to meet the challenge of forewarning tsunamis.