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Ring Of Fire Strikes Again In Indonesia
Hong Kong (AFP) March 6, 2007 A powerful earthquake Tuesday that rocked Indonesia's island of Sumatra again showed the ferocity of the "Ring of Fire", a massive zone of instability that encircles the Pacific. Most of history's deadliest quakes, tremors and volcanic explosions have occurred along this weak line in the Earth's crust, including the eruptions of Krakatoa near Java and Mount St Helens in the United States, as well as the quake that set off the devastating Indian Ocean tsunami in December 2004. The Ring stretches along the western coast of the Americas, through the island nations of the South Pacific and on through Southeast Asia. It is an interconnected circle of fault lines -- cracks in the Earth's hardened upper crust -- which are under constant pressure from super-hot molten rock beneath. Occasionally the fissures give in to the pressure and explode, creating volcanic eruptions or causing the land either side of the fault line to shift and buckle violently, triggering earthquakes. The fault lines are actually the margins of huge plates of rock on which the continents sit. These plates are in constant motion. Quake expert Gary Gibson said that while the full toll of Tuesday's quakes was not yet known, the death count could end up lower than might have been expected. "This was in a different part of the seismic zone to the previous big earthquakes -- it was inland and not at sea," said Gibson, professor of seismology at RMIT University in Melbourne, Australia. "Inland quakes are shallower and therefore their energy is greater and spread over a greater area," he said. Tuesday's quake was felt in Singapore, about 430 kilometres (265 miles) away. Most of the region's seismic events are small and occur under the sea, where the majority of the continental plate margins are found. According to the US Geological Survey, which studies seismic activity, there has been an average of 19.4 quakes of 7.0-plus strength on the Ring each year. "Big quakes like these happen all the time -- they only become news when they happen in places with large populations," said Gibson. "Unfortunately, the death tolls in the quakes in this region are usually high because the fault lines run through some of the most densely populated cities in Asia," he said. Indonesia has suffered from three catastrophic earthquakes in slightly more than two years. The 9.3-magnitude quake on December 26, 2004 unleashed tsunamis that crashed into Indian Ocean shorelines and killed 168,000 in Indonesia's Aceh province alone. Some 5,800 people were killed and 33,000 others injured in a quake on Java island in May last year. Two months later, another quake on Java killed more than 600.
Source: Agence France-Presse Related Links When the Earth Quakes Tectonic Science and News
Gauging Earthquake Hazards Through Study Of Precariously Balance Rocks
Reno NV (SPX) Mar 05, 2007A seismological research team from the University of Nevada, Reno is finding ways to make precariously balanced rocks talk. In so doing, they are unlocking valuable scientific information in assessing seismic hazards in areas throughout the West. Their findings are shared in the January-February issue of American Scientist magazine. Scientists believe that zones of precarious rocks - rocks that have come close but haven't tipped over in the wake of a major seismic event - provide important information about seismic risk, its magnitude and its frequency. |
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