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How do they spread?
April 13, 2009Uneven propagation of Earth quake waves
Propagation of earthquake waves within the Earth is not uniform. Experiments indicate that the velocity of shear waves (s-waves) in Earth's lower mantle between 660 and 2900 km depth is strongly dependent on the orientation of ferropericlase. In the latest issue of "Science" (Vol. 325, 10.04.2009), researchers from the German Research Center for Geosciences GFZ, the Karlsruhe Institute of Technology, the University of Bayreuth, and Arizona State University report unexpected properties of ferropericlase, which is presumably the second most abundant mineral of the lower mantle.
"The dependence of wave velocity on direction increases significantly at a pressure of about 50 Giga-Pascal, corresponding to approximately 1300 km depth. This is caused by a change in electronic arrangement of the iron ions in ferropericlase" explains Hauke Marquardt from GFZ. In addition, flow in the lower mantle results in a preferred mineral orientation; this causes the detectable non-uniform propagation of earthquake waves. This flow is the driving force of tectonic plate movements, formation of mountains, earthquakes, and volcanic activities and therefore, strongly affects our life on Earth's surface.
Because the deep interior of our planet is not accessible to direct observations, the researchers simulate the conditions of Earth's interior by generating the extreme pressures in their laboratory. Diamond anvil cells are used at GFZ to perform the high-pressure experiments, which are complemented by X-ray diffraction experiments at "Diamond Light Source" in Didcot, UK.
These new findings are of practical importance: Only if we know the properties of the materials that constitute the deep Earth, we can derive information about its internal flow from the non-uniform propagation of earthquake waves. This can help to better understand plate tectonic processes.
Helmholtz Association of German Research Centres
Because the deep interior of our planet is not accessible to direct observations, the researchers simulate the conditions of Earth's interior by generating the extreme pressures in their laboratory. Diamond anvil cells are used at GFZ to perform the high-pressure experiments, which are complemented by X-ray diffraction experiments at "Diamond Light Source" in Didcot, UK.
These new findings are of practical importance: Only if we know the properties of the materials that constitute the deep Earth, we can derive information about its internal flow from the non-uniform propagation of earthquake waves. This can help to better understand plate tectonic processes.
Helmholtz Association of German Research Centres
Earthquake Waves Current Events and Earthquake Waves News RSSListening to rocks helps researchers better understand earthquakes
When Apollo punished King Midas by giving him donkey ears, only the king and his barber knew. Unable to keep a secret, the barber dug a hole, whispered into it, "King Midas has donkey ears," and filled the hole. But plants sprouted from the hole, and with each passing breeze, shared the king's secret.
Supercomputer Unleashes Virtual 9.0 Megaquake in Pacific Northwest
On January 26, 1700, at about 9 p.m. local time, the Juan de Fuca plate beneath the ocean in the Pacific Northwest suddenly moved, slipping some 60 feet eastward beneath the North American plate in a monster quake of approximately magnitude 9, setting in motion large tsunamis that struck the coast of North America and traveled to the shores of Japan.
2002 Alaskan quake left 7 areas of California stirred but not shaken
Earth tremors not linked to volcanic activity first turned up in seismic observations several years ago, but those tremors were almost exclusively in subduction zones such as the Cascadia region off the coast of the Pacific Northwest.
Arizona State University geophysicists detect a molten rock layer deep below the American Southwest
A sheet of molten rock roughly 10 miles thick spreads underneath much of the American Southwest, some 250 miles below Tucson, Ariz. From the surface, you can't see it, smell it or feel it.
A century after 1906 earthquake, geophysicists revisit 'Big One' and come up with new model
Almost a century after the 1906 earthquake, Stanford geophysicists have revisited San Francisco's ''Big One'' and now paint a new picture of a fault that was ready to go and that ruptured farther and faster than previously supposed.
WAVES IN STELLAR ATMOSPHERES
ROYAL ASTRONOMICAL SOCIETY PRESS NOTICE:
Starquakes reveal stellar secrets
Looking into the interior of the Earth or the Sun is a bit similar to examining a baby in its mother`s womb using an ultrasound scan. Light cannot penetrate the area, so we make pictures in these cases using sound waves, which human ears cannot hear. With SOHO, ESA has probed deeply into the Sun using the sound-waves principle, and with great success. The future missions, Solar Orbiter and Eddington, will look inside our Sun and other stars, respectively, in a similar way. Here on Earth, when scientists recorded slight shakes, or seisms, coming from earthquakes even on distant continents, they began to estimate the routes and the changing speeds of the waves passing through the Earth`s inter
Violent days on the Sun
On Tuesday 23 July 2002 space scientists recorded the largest of four powerful solar flares, all occurring in the space of just eight days. Solar flares are tremendous explosions in the atmosphere of the Sun, with the most powerful class, called the X class, capable of releasing as much energy as a thousand million megatonnes of high explosive. Solar astronomers watch flares closely because they can disrupt high-technology systems. The Solar and Heliospheric Observatory (SOHO) spacecraft gave a preview of the stormy solar weather even while it was still rumbling on the far side of the Sun, the side opposite the Earth. The flares came from sites of violent activity on the Sun, called activ
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