The Hindu : International : Tsunami warning system in place elsewhere

Online edition of India's National Newspaper
Tuesday, Dec 28, 2004

International

International

Tsunami warning system in place elsewhere

DENVER, DEC. 27. The toll in Asia caused by a massive tsunami might have been lower had India and Sri Lanka been part of an international warning system designed to warn coastal communities about potentially deadly waves, scientists say.

There are 26 countries that make up the International Coordination Group for the Tsunami Warning System.

The system predicts where tsunamis will strike up to 14 hours in advance. It relies on a network of earthquake seismic sensors and tidal gauges attached to buoys in the oceans. However, the network's western edge stops near Thailand and Singapore and does not extend into the Indian Ocean.

The members of the Tsunami warning system are: Australia, Canada, Chile, China, Columbia, Cook Islands, Costa Rica, Ecuador, Fiji, France (because it controls French Polynesia and other island territories), Guatemala, Indonesia, Japan, Mexico, New Zealand, Nicaragua, North Korea, Peru, Philippines, Russia, Singapore, South Korea, Thailand, Hong Kong, United States and Western Samoa.

Early warning

The warning system is designed to alert nations that potentially destructive waves may hit their coastlines within three to 14 hours. Scientists said seismic networks recorded Sunday's massive earthquake, but without wave sensors in the region, there was no way to determine the direction a tsunami would travel.

A single wave station south of the earthquake's epicentre registered tsunami activity less than 60 cm high heading south toward Australia, researchers said. Although Thailand belongs to the international tsunami-warning network, its west coast does not have the system's wave sensors mounted on ocean buoys.

The northern tip of the earthquake fault is located near the Andaman and Nicobar Islands, and tsunamis appear to have rushed eastward toward the Thai resort of Phuket.

"They had no tidal gauges and they had no warning," said Waverly Person, a geophysicist at the National Earthquake Information Centre in Golden, Colorado, U.S., which monitors seismic activity worldwide. "There are no buoys in the Indian Ocean and that's where this tsunami occurred."

Fault near Andamans

The earthquake broke on a fault line deep off the Sumatra coast, running north and south for about 965 km or as far north as the Andaman and Nicobar islands.

"It's a huge rupture," said Charles McCreery, director of the Pacific Tsunami Warning Centre near Honolulu. "It's conceivable that the sea floor deformed all the way along that rupture, and that's what initiates tsunamis."

Tsunamis as large and destructive as Sunday's typically happen only a few times in a century. A tsunami is not a single wave, but a series of travelling ocean waves generated by geological disturbances near or below the ocean floor.

With nothing to stop them, these waves can race across the ocean like the crack of a bullwhip, gaining momentum over thousands of kilometres. Most are triggered by large earthquakes but they can be caused by landslips, volcanoes and even meteor impacts. The waves are generated when geologic forces displace seawater in the ocean basin. The bigger the earthquake, the more the earth's crust shifts and the more seawater begins to move.

— AP

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