ScienceDaily — A new study evaluates expected ground motion in Seattle, Victoria and Vancouver from earthquakes of magnitude 7.5 - 9.0, providing engineers and policymakers with a new tool to build or retrofit structures to withstand seismic waves from large "subduction" earthquakes off the continent's west coast. The Cascadia subduction zone in the Pacific Northwest has produced great earthquakes of magnitude 9.0 and larger, most recently in the 1700s. Now home to millions of people and a vast infrastructure of buildings and other man-made structures, scientists seek to determine the impact of large earthquakes on the region.
To simulate ground motions from a very large earthquake on the local region, this study combined detailed analysis of ground motions recorded from smaller earthquakes in the Pacific Northwest with recorded data from a severe subduction earthquake from another region - the M8.4 2003 Tokachi-Oki quake off the coast of Japan. The authors estimate ground motions for firm ground at the three sites and provide a model that engineers can adjust for local or site-specific soil conditions.
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Sunday, June 14, 2009
Predicted Ground Motions For Great Earthquake In Pacific Northwest: Seattle, Victoria And Vancouver
Typhoons trigger slow earthquakes
By Victoria Gill, Science reporter, BBC News
The researchers believe this could explain why there are relatively few large earthquakes in this region. Alan Linde from the Carnegie Institution for Science in the US and colleagues monitored movement of two colliding tectonic plates in eastern Taiwan.
Asteroid Probe Set to "Collide" With Earth
Julian Ryall in Tokyo for National Geographic News
The Hayabusa spacecraft is currently on its way back to Earth after a successful mission that landed on and hopefully collected samples from the asteroid Itokawa. Potential samples will be aboard a heat-resistant capsule that will separate from Hayabusa shortly before re-entry into Earth's atmosphere so they can be recovered.
But experts say the main body of the craft will most likely disintegrate during the trip through Earth's atmosphere.
Although the plan was not part of Hayabusa's original mission, scientists at the Japan Aerospace Exploration Agency (JAXA) recently decided to make the most of the doomed probe's return.
"Even though Hayabusa is not actually an asteroid, it will be on a path that will cause it to collide with the Earth in the same way as an asteroid," said JAXA spokesperson Akinori Hashimoto.
"We will monitor its movements, and the data will enable us to accurately predict the future paths of asteroids that are on course to come close to the Earth."
Greece suffers summer fires
Firefighters are battling wildfires in the centre of Greece that have burnt through forest, farmland and vineyards and threatened homes. The outbreak on Saturday, several kilometres from the city of Thebes, is being fought on four fronts and caused black smoke to be seen in the sky for miles. Farmers and residents were told to evacuate the area, although no casualties were immediately reported. The fires were pushed towards the town of Ritsona, north of Athens, the capital, by strong winds. Police have closed part of a highway leading to Athens.
It is the first fire in Greece this summer and broke out after temperatures reached 30 degrees Celsius. Two years ago the country suffered some of its worst fires in decades, in which at least 67 people were killed and scores of homes were destroyed.
