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Samoa quakes may have been connected TRENDS Prof Yash
Pal THIS UNIVERSE |
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Samoa quakes may have been connected
Earthquakes
are one of the most violent and unpredictable forces of nature and a huge amount of scientific effort has gone into studying the factors that can trigger the sudden ground movements leading to the sort of death and destruction seen in Indonesia and the South Pacific. In general, earthquakes occur on a geological fault line where two or more immense slabs of rock grind up against one another as part of the global tectonic movements of the Earth’s crust. When friction causes this grinding motion to get stuck, the resulting build-up of stress can be released suddenly as an earthquake – a slip along the geological fault line. One of the unanswered questions is whether yesterday’s devastating earthquake off the coast of the Indonesian island of Sumatra, near the city of Padang, was in any way connected to the earlier quake that killed up to 100 people on the Pacific island of Samoa. The answer could turn out to be “yes”. A study published in the journal Nature has found that an earthquake at one fault can affect the strength of another fault line else-where in the world. The study did not, of course, look at the latest earthquakes, but investigated the effects of two earlier quakes – the 1992 Landers earthquake in California and the 2004 earthquake off Sumatra that resulted in the devastating tsunami that killed 230,000 people around the coasts of Thailand and Indonesia and across the Indian Ocean. The seismologists found that both of these earthquakes had affected the strength of the San Andreas fault in California, which is the most studied fault line in the world. In other words, a large earthquake in one part of the world can affect the strength, and therefore the probability of a subsequent earthquake on a fault line in another part of the world. A fault line’s strength could turn out to be important in terms of predicting future earthquakes, but until now it has not been possible to measure it in any meaningful way. The American seismologists behind the latest study got round the problem by monitoring fluid-filled fractures deep within the San Andreas fault zone nearly two miles below the surface. It is possible that the fluid in these fractures can act as a lubricant within the fault, thereby weakening the fault line’s strength by making it more “slippy”, and so increasing the likelihood of an earthquake. By monitoring these fluid-filled fractures with highly sensitive seismic instruments, it may be possible to detect critical changes to the strength of the fault just prior to a quake. The scientists, led by Taka’aki Taira and the late Paul Silver of the Carnegie Institution for Science in Washington, believe that monitoring the movements of these fluid-filled fractures can become a proxy for measuring the strength of a geological fault. They said it may be possible one day to detect the sort of changes that occur before an earthquake strikes – in other words a method of earthquake prediction. “Fault strength is a fundamental property of seismic zones. Earthquakes are caused when a fault fails, either because of the build-up of stress or because of a weakening of the fault,” Dr Taira said. “Changes in fault strength are much harder to measure than changes in stress, especially for faults deep in the crust. Our result opens up exciting possibilities for monitoring seismic risk and understanding the causes of earthquakes,” he said. But an equally intriguing conclusion of this study is that a fault line’s strength can be affected by an earthquake many hundreds or even thousand of miles away – as far away as Sumatra is from California for example – according to team member Fenglin Niu of Rice University in Houston, Texas. “It is possible that the strength of faults and earthquake risk is affected by seismic events on the other side of the world,” Dr Niu said. This finding could explain why the earthquake off Sumatra yesterday occurred just hours after another earthquake and its tsunami hit
Samoa.
— By arrangement with
The Independent |
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Two meter sea level rise
unstoppable
OXFORD, England: A rise of at least two meters in the world’s sea levels is now almost unstoppable, experts told a climate conference at Oxford University on Tuesday. “The crux of the sea level issue is that it starts very slowly but once it gets going it is practically unstoppable,” said Stefan Rahmstorf, a scientist at Germany’s Potsdam Institute and a widely recognized sea level expert. Canadian
circus tycoon makes journey into space BAIKONUR, Kazakhstan: Canadian circus billionaire Guy Laliberte blasted off in a Russian Soyuz spaceship from Kazakhstan on Wednesday to become the world’s seventh space tourist. The 50-year-old former fire-breather and founder of the Montreal-based Cirque du Soleil gave the thumbs-up after the Soyuz TMA-16 spaceship blasted into clear blue skies in a faultless launch at 0714 GMT from the Baikonur cosmodrome on the Kazakh steppe. China finds bird-like dinosaur
with four wings HONG KONG:
Chinese researchers have unearthed the fossil of a bird-like dinosaur with four wings in northeastern China, which they suggest is a missing link in dinosaurs’ evolution into birds. In a paper in the journal Nature, they said they found the well-preserved fossil of the “Anchiornis huxleyi,” which roamed the earth some 160 million years ago, in China’s northeastern Liaoning province. LONDON: Detailed data about the smallest planet ever found outside our solar system suggest it is a rocky “super-Earth” world very like our own, European astronomers say. The so-called exoplanet, whose initial discovery was announced in February, has a mass five times that of Earth, which when combined with its radius suggests it has a solid surface and a density similar to our terrestrial home.
— Reuters |
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THIS UNIVERSE Is there any method to separate a
mixture of water, salt and sugar? This is a hard one. Some chemical routes might work, but seem messy. One of the things suggested is to dissolve the sugar in liquid paraffin — essentially something like petroleum. I doubt if you would like to sweeten your tea with the sugar you get after evaporating all the solvent. Salt might be easier, but I would like some good chemist to come in here. Is it true that unexplained happenings occur in the Bermuda Triangle? The stories and fiction of the Bermuda Triangle have been carefully analysed. There is no evidence that the rate of marine accidents in that area is higher than would be expected for any hurricane-prone area. It has been shown and demonstrated that the whole thing is a media invention. People like mysteries and elaboration of this mystery has sold a lot of books and magazines, and has spawned many films. Where are the poles of a spherical magnet? I am quoting below a reply I gave to this question over five years ago. I suggest that questioners might benefit by consulting The Tribune archives. “The magnets you are familiar with are produced by aligning the microscopic magnetic domains of a magnetic material. We assign magnetic moments even to individual charged particles whenever they have a spin angular momentum. Nuclei of atoms also have spins. Think of them as tiny magnets that, in a non-magnetised state of the bulk material, are randomly oriented. Magnetisation is a process of alignment. Therefore for a magnet in a spherical shape the poles would be positioned depending on the way the sphere was magnetised. It might happen, though, that in an irregular shaped material, internal interaction between domains might produce a localised unpredictability in the magnetic
field.” Readers wanting to ask Prof Yash Pal a question can e-mail him at palyash.pal@gmail.com |
