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Indian Ocean tsunami risk and early warning system requirement

Compared to the Pacific Ocean , which hosts 80 percent of all recorded tsunami, the Indian Ocean is rarely host to destructive and/or lethal tsunami. The last major event occurred in 1883 when pyroclastic flows generated by the 1883 eruption of Krakatoa triggered tsunami up to 40 m high, which caused widespread destruction and took close to 40,000 lives along the coasts of southern Sumatra and eastern Java. Significant earthquake triggered tsunami in the Sumatra region are reported for 1797, 1833, 1843 and 1861. The absence of a major event since the middle of the 19 th century was certainly a contributory factor in the recent decision by governments in the region NOT to develop a tsunami warning system for the Indian Ocean . As is often the case, development of such early warning systems is typically reactive rather than proactive, and the Pacific Tsunami Warning System, which has been operational since 1965, was put together in response to major tsunamigenic earthquakes in Chile (1960) and Alaska (1964). While tsunami travel times from one side of the Pacific to the other are on the order of 10 to 20 hours, thereby maximising time for warning dissemination and evacuation, the smaller dimensions of the Indian Ocean result in cross-basin travel times of only 8 to 12 hours. In the case of the Boxing Day tsunami, the waves reached the coast of Indonesia 's Aceh province in less than 30 minutes, and the Phuket region of Thailand , the east coast of Sri Lanka and SE India in around 2 hours. The waves reached Somalia seven to eight hours after the quake.

Despite the reduced travel times, an extant early warning system could have saved tens of thousands of lives in Thailand, Sri Lanka, southern India and further afield. Notwithstanding the relative paucity of major tsunami events in the Indian Ocean , it is critical that the most is made of the current window of opportunity to establish an effective warning system for the basin. There is some evidence of the clustering of major quakes in the region and a possibility that another large, tsunamigenic event could arrive within decades rather than centuries. The technology required - a system of ocean-floor pressure sensors linked via satellite to provide tsunami warnings to emergency managers in the countries at risk - is well established. More critical to the successful operation of a warning system is an effective means of rapid dissemination of the warning to the affected populations. Ensuring that people understand the message and act upon it immediately will require a concerted and continuing education campaign accompanied by an unambiguous and multi-media warning signal, which may include everything from officials on bicycles blowing whistles or in cars with megaphones, to sirens, to radio and television broadcasts and text messages.

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