Hi All. It appears the Sumatra quake has scientists rethinking about the larger quakes. Take Care…Don in creepy town

“Boulder, Colo. - The risks of Sumatra-style mega-quakes around the world have been sorely misjudged, say earth scientists who are re-examining some of the pre-December 2004 assumptions scientists made about such rare events.”

“For more than two decades geologists had thought that the largest quakes, of magnitude 9 and greater, happen when a young tectonic plate is subducted, or shoved quickly, under another plate. But the Great Sumatra-Andaman earthquake of 26 December 2004 didn't match that pattern at all. The Indian Plate is middle-aged and moving at a middling rate, which throws into question the estimated quake dangers at other similar quake-prone zones near Japan, in the Pacific Northwest, Chile, Alaska, and elsewhere.”

"We didn't expect such a big earthquake in that location," said Emile Okal of Northwestern University. Okal is slated to speak about how the Sumatra-Andaman quake calls into question theoretical assumptions made about other similar dangers zones worldwide and especially in South America on Thursday, 6 April, at Backbone of the Americas - Patagonia to Alaska. The meeting is co-convened by the Geological Society of America and Asociación Geológica Argentina, with collaboration of the Sociedad Geológica de Chile. The meeting takes place 3-7 April in Mendoza, Argentina.”

“Previous to the catastrophic 26 December 2004 earthquake, the theory about how subduction zones generate quakes was straightforward, says Okal. It boiled down to age and speed. Where an older, colder and therefore denser slab of crust is being pushed slowly under another plate, "It will want to sink," he said. As a result there's not a lot of stress building up to cause large quakes.”

• Sumatra Quake