Important Historical Events
Warning signs of the 2004 Asia earthquake and resulting tsunami disaster.
Despite a lag of up to several hours between the earthquake and the impact of the tsunamis, nearly all of the victims were taken completely by surprise. This is because there is no tsunami warning system in the Indian Ocean to detect tsunamis, and equally importantly, warn the general populace living around the ocean quickly. Tsunami detection is not easy because while a tsunami is in deep water it has a very low 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.
Scientists were also hampered by the fact that the initial estimate for the magnitude of the earthquake was 8.1. The determination that the earthquake had actually been much stronger (and the resulting tsunami much larger) was not made until after the tsunamis had already struck.
Tsunamis usually occur in the Pacific Ocean due to earthquakes in the "Ring of Fire", and an effective tsunami warning system has long been in place there. Although the extreme western edge of the "Ring of Fire" extends into the Indian Ocean (the point where this earthquake struck), no warning system exists in that ocean due to the rarity of tsunamis there — the last major one was caused by the Krakatoa eruption of 1883.
In the aftermath of the disaster there is a new awareness of the need for a tsunami warning system for the Indian Ocean. The UN aims to have a working East Asia and Southeast Asia early warning system within a year. Some have even proposed creating a unified global tsunami warning system, to include the Atlantic Ocean and Caribbean.
Unfamiliarity with warning signs
The first warning sign of a possible tsunami is the earthquake itself; however tsunamis can strike thousands of miles 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. People in Pacific regions are more familiar with tsunamis and often recognize this phenomenon as a sign to head for higher ground. However, 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 of exposed beach, with fatal results.
One of the few coastal areas to evacuate ahead of the tsunami was on the Indonesian island of Simeulue, very close to the epicentre. Island folklore recounted an earthquake and tsunami in 1907 and the islanders fled to inland hills after the initial shaking — before the tsunami struck. On Maikhao beach in northern Phuket, Thailand, a 10 year old British girl named Tilly Smith had studied tsunamis in geography class at school and recognised the warning sign of the receding ocean. She and her parents warned others on the beach, which was evacuated safely.