<P> Because the 1,600 km (1,000 mi) fault affected by the earthquake was in a nearly north - south orientation, the greatest strength of the tsunami waves was in an east - west direction . Bangladesh, which lies at the northern end of the Bay of Bengal, had very few casualties despite being a low - lying country relatively near the epicenter . It also benefited from the fact that the earthquake proceeded more slowly in the northern rupture zone, greatly reducing the energy of the water displacements in that region . </P> <P> 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 state of Kerala was hit by the tsunami despite being on the western coast of India, and the western coast of Sri Lanka suffered substantial impacts . Distance alone was no guarantee of safety, as Somalia was hit harder than Bangladesh despite being much farther away . </P> <P> Because of the distances involved, the tsunami took anywhere from fifteen minutes to seven hours to reach the coastlines . The northern regions of the Indonesian island of Sumatra were hit very quickly, while Sri Lanka and the east coast of India were hit roughly 90 minutes to two hours later . Thailand was struck about two hours later despite being closer to the epicentre, because the tsunami traveled more slowly in the shallow Andaman Sea off its western coast . </P> <P> The tsunami was noticed as far as Struisbaai in South Africa, some 8,500 km (5,300 mi) away, where a 1.5 m (5 ft) high tide surged on shore about 16 hours after the earthquake . It took a relatively long time to reach Struisbaai at the southernmost point of Africa, probably because of the broad continental shelf off South Africa and because the tsunami would have followed the South African coast from east to west . The tsunami also reached Antarctica, where tidal gauges at Japan's Showa Base recorded oscillations of up to a metre (3 ft 3 in), with disturbances lasting a couple of days . </P>

How long did the tsunami in thailand last