FRENCH POLYNESIA DISTANT TARGET FOR TSUNAMIS

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PAPEÉTE, Tahiti (Tahitipresse, Jan. 5) - While French Polynesia may be subject to more tsunamis, the French West Indies face a far greater risk of potential heavy tsunami damage, according to French experts interviewed by Agence France-Presse.

The sprawling islands and atolls of French Polynesia are located in the Pacific, a region that produces 90 percent of the world’s tsunamis. But the French overseas territory is not located in a "subduction zone," an area in which one tectonic plate is being pushed under another plate, resulting in a huge earthquake such as the devastating magnitude 9 "great quake" that occurred in the Indian Ocean on December 26.

French Polynesia is threatened "every 10 or 20 years" by "tsunami waves coming from distant earthquakes," Marc-André Gutscher, a geophysicist at the Oceanic Domaines Laboratory of the French National Scientific Research Center (CNRS), told AFP.

And such tsunami waves are relatively weak, being about two to four meters (6.6-13 feet) high, their force depending on various factors, such as the time of day, whether the tide is in or out and the origin of the tsunami.

The epicenter of an earthquake causing a tsunami to travel to French Polynesia could be as far away as 5,000 or 8,000 kilometers (3,107-4,971 miles). That would involve an earthquake in South America, Japan, the Aleutian Islands between Alaska and Siberia or at Kamchatka in far eastern Russia.

So a tidal wave created by a magnitude 8, earthquake on the Richter scale that hit Chile on July 30, 1995 resulted in a four-meter-high wave that arrived in the Marquesas Islands and caused property damage to this northernmost archipelago of French Polynesia.

By comparison, the French overseas departments of Martinique and Guadeloupe are located "directly over a subduction zone," where the North American plate is pushing under the Caribbean plate. The two islands are thus likely to be hit "approximately every 200 years" by underwater quakes with epicenters only some 100 kilometers (62 miles) away.

If such an earthquake reached a magnitude of 8, it would cause "heavy damage", Gutscher said. It would "probably" generate a tidal wave "with waves from five to 10 meters" (16-33 feet). Education of the populations is fundamental, he said. In the French West Indies, they would have two signals of alarm, the initial jolt and 10 to 20 minutes later a "negative wave" such as what was produced along several Southeast Asian coasts on December 26 when the ocean movement began by ebbing before brutally returning.

The French Ecology Ministry in Paris told AFP that information and education were important to lessen earthquake consequences, regardless if the epicenter is under an ocean or underground. The ministry also noted that the same magnitude of an earthquake today would be far more devastating than in the past due to greater urbanization and construction methods involving lighter houses and taller buildings.

As a result, the earthquake that devastated Fort-de-France, Martinique, in 1839 would today claim 4,700 lives, compared to 300 at the time, the ministry said. The magnitude 7.5 earthquake that hit Pointe-à-Pitre, Guadeloupe, in 1843 would cause 10,300 deaths today, compared with only 2,000 at the time.

January 6, 2005

Tahitipresse: www.tahitipresse.pf

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