[5] It was one of the deadliest natural disasters in recorded history. Indonesia was the hardest hit, followed by Sri Lanka, India, and Thailand. With a magnitude of between 9. 1 and 9. 3, it is the third largest earthquake ever recorded on a seismograph.
This earthquake had the longest duration of faulting ever observed, between 8. nd 10 minutes. It caused the entire planet to vibrate as much as 1 cm (0. 4 inches)[6] and triggered other earthquakes as far away as Alaska.
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[7] Its hypocenter was between Simeulue and mainland Indonesia. [8] The hypocentre of the main earthquake was approximately 160 km (100 mi), in the Indian Ocean just north of Simeulue island, off the western coast of northern Sumatra, at a depth of 30 km (19 mi) below mean sea level (initially reported as 10 km).
The northern section of the Sunda megathrust, which had been assumed dormant, ruptured; the rupture having a length of 1300 km. ] The size of the rupture caused plate shifting of up to 20 m,[citation needed] causing the earthquake (followed by the tsunami) to be felt simultaneously as far away as Bangladesh, India, Malaysia, Myanmar, Thailand, Singapore and the Maldives. Seismographic and acoustic data indicate that the first phase involved a rupture about 400 km (250 mi) long and 100 km (60 mi) wide, located 30 km (19 mi) beneath the sea bed—the largest rupture ever known to have been caused by an earthquake.
The rupture proceeded at a speed of about 2. 8 km/s (1. i/s) or 10,000 km/h (6,300 mph), beginning off the coast of Aceh and proceeding north-westerly over a period of about 100 seconds. The sudden vertical rise of the seabed by several metres during the earthquake displaced massive volumes of water, resulting in a tsunami that struck the coasts of the Indian Ocean. A tsunami which causes damage far away from its source is sometimes called a teletsunami and is much more likely to be produced by vertical motion of the seabed than by horizontal motion. [ The tsunami, like all others, behaved very differently in deep water than in shallow water.
In deep ocean water, tsunami waves form only a small hump, barely noticeable and harmless, which generally travels at a very high speed of 500 to 1,000 km/h (310 to 620 mph); in shallow water near coastlines, a tsunami slows down to only tens of kilometres an hour, but in doing so forms large destructive waves. Scientists investigating the damage in Aceh found evidence that the wave reached a height of 24 m (79 ft) when coming ashore along large stretches of the coastline, rising to 30 m (98 ft) in some areas when travelling inland. ]
Radar satellites recorded the heights of tsunami waves in deep water: at two hours after the earthquake, the maximum height was 60 centimetres (2. 0 ft). These are the first such observations ever made. Unfortunately these observations could not be used to provide a warning, since the satellites were not built for that purpose and the data took hours to analyze. [38][39] Coasts that have a landmass between them and the tsunami’s location of origin are usually safe; however, tsunami waves can sometimes diffract around such landmasses.
Thus, the Indian state of Kerala was hit by the tsunami despite being on the western coast of India, and the western coast of Sri Lanka also suffered substantial impacts. Also distance alone was no guarantee of safety; Somalia was hit harder than Bangladesh despite being much farther away.
Despite a lag of up to several hours between the earthquake and the impact of the tsunami, nearly all of the victims were taken completely by surprise. There were no tsunami warning systems in the Indian Ocean to detect tsunamis or to warn the general populace living around the ocean.
Tsunami detection is not easy because while a tsunami is in deep water it has little height and a network of sensors is needed to detect it. Setting up the communications infrastructure to issue timely warnings is an even bigger problem, partiIn the aftermath of the disaster, there is now an awareness of the need for a tsunami warning system for the Indian Ocean. The United Nations started working on an Indian Ocean Tsunami Warning System and by 2005 had the initial steps in place. Some have even proposed creating a unified global tsunami warning system, to include the Atlantic Ocean and Caribbean.
In the aftermath of the disaster, there is now an awareness of the need for a tsunami warning system for the Indian Ocean. The United Nations started working on an Indian Ocean Tsunami Warning System and by 2005 had the initial steps in place. Some have even proposed creating a unified global tsunami warning system, to include the Atlantic Ocean and Caribbean. The first warning sign of a possible tsunami is the earthquake itself. However, tsunami can strike thousands of kilometres away where the earthquake is only felt weakly or not at all.
Also, in the minutes preceding a tsunami strike, the sea often recedes temporarily from the coast. Around the Indian Ocean, this rare sight reportedly induced people, especially children, to visit the coast to investigate and collect stranded fish on as much as 2. 5 km (1. 6 mi) of exposed beach, with fatal results. [46] However, not all tsunami causes this “disappearing sea” effect. In some cases, there are no warning signs at all: the sea will suddenly swell without retreating, surprising many people and giving them little time to flee.
The tsunami caused serious damage and deaths as far as the east coast of Africa, with the furthest recorded death due to the tsunami occurring at Rooi Els in South Africa, 8,000 km (4,971 mi) away from the epicentre. In total, eight people in South Africa died due to abnormally high sea levels and waves. Distruction Tsunami causes destruction primarily due to the ultrahigh impacts on structures and other assets. The basic factors of destruction include, wave impact, erosion , and inundation. The drag applied by tsunami waves on structures can move them or overturn them.
The presence of high salt concentration in tsunami waves causes corrosion of metallic bodies, which decreases their life ultimately leading to failure. As tsunami causes large scale structural destruction, the floating debris so formed poses serious threat to other structures, or floating vessels. Besides the primary destruction, secondary destruction may include fire hazards, and water pollution. Fire hazards may be caused by severed electricity transmission lines, while damaged oil tankers may contribute a serious threat to water quality. Rescue The tsunami brought about the devastation of transport and communication infrastructure.
Roads were destroyed, blocking off access via land to some affected areas. Thus, aerial and sea military transports were required to reach some rural areas. Helicopters are especially effective in the search and rescue operations. They do not require landing runways, and they provide a good view for rescuers. Thus, rescuers are able to spot injured survivors, and evacuate them to safety. The force of the tsunami has altered the landscape of coastal areas, rendering most conventional topological maps useless. Therefore, ships with radar capabilities play supporting roles by coordinating the operations, and carrying out surveillance work.
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