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Japan's 2011 megaquake reactivated dormant faults
corbis/ap photo/david guttenfelder
IN BRIEF Honesty is always the best policy
Japan’s megaquake reactivated dormant faults The megaquake that shook the east coast of Japan in March 2011 reactivated dormant faults near Fukushima’s beleaguered nuclear reactors, geologists warn. “A strong quake may occur in the Futaba fault, only 5 to 6 kilometres away,” says Dapeng Zhao of Tohoku University. The fault runs parallel to the coast, right past both of Fukushima’s nuclear plants. Zhao’s team used data from more than 6000 quakes between June 2002 and October 2011 to make a 3D map of the crust in the area that suffered the largest aftershock recorded on land after the March megaquake:
a quake on 11 April in Iwiki. The images show fluid rising through the Pacific plate as it sinks under Japan. They say the March quake transferred stress to surrounding faults, causing them to adjust in aftershocks. The fluid in the Iwiki fault lubricated it, causing it to slip almost immediately in a large, magnitude 7 aftershock (Solid Earth, DOI: 10.5194/se-3-43-2012). Seismic readings from the Fukushima area reveal stresses and rising fluids similar to those found at Iwiki, so “the possibility of quake generation becomes much larger than before the 11 March quake”, says Zhao. A magnitude 7 quake would release far less energy than the magnitude 9 megaquake, but because the Futaba fault is so close to Fukushima, it would shake both power stations more strongly.
One-size-fits-all star clusters WHY do the universe’s oldest star clusters tend to be roughly the same size? The answer is grizzly. Globular star clusters are ancient, spherical blobs of stars. Most of these clusters are a few hundred thousand times the mass of our sun. The scarcity of much bigger clusters is no surprise as there must be an upper limit – but why are there so few small ones?
Using computer modelling, Diederik Kruijssen of the Max Planck Institute for Astrophysics in Garching, Germany, and his colleagues simulated the merger of two small galaxies. This process is thought to have been especially common in the early universe, when small structures were busy snowballing into larger ones. The collision compressed gas into dense knots, sparking star
formation and creating many new globular clusters. At the same time it seeded destruction, as the gravity of these knots disrupted clusters – both existing and new – passing nearby. Medium and large clusters survived, bound by their own strong gravity, but the smaller ones were ripped apart (arxiv.org/abs/1112.1065). All big galaxies probably formed in such mergers so this might be why globular clusters fall into such a narrow size range.
CHEATERS never prosper – at least not in the lab. A new finding contradicts the notion that cooperative organisms are vulnerable to freeloaders. Some bacteria send out signals that help a lab culture as a whole adapt to its environment, so other bugs ought to be able to benefit without wasting any of their own resources on signals. David Van Dyken at the University of British Columbia in Vancouver, Canada, studied the genetics of bacterial cultures and found this wasn’t true. Surprisingly, no known “cheating” genotype was common enough to suggest that it was an old-timer in the culture. Instead, cheaters are present simply because they arise through mutation faster than natural selection can purge them from the population. Cheating may not be a stable strategy (American Naturalist, DOI: 10.1086/664609).
Did early ungulate use echolocation? ONE of the first mammals to use echolocation may not have been a bat or a whale, but an early ancestor of horses. Hyopsodus was a weasel-like ungulate that lived 55 million years ago, around the time that bats evolved echolocation. Maéva Orliac of Montpellier University, France, and colleagues say that a new fossil cast of its braincase shows Hyopsodus had a large inferior colliculus, a brain region enlarged in echolocating animals (PLoS One, DOI: 10.1371/ journal.pone.0030000). They argue that Hyopsodus could echolocate, but Gregg Gunnell at Duke University in Durham, North Carolina, says the large inferior colliculus may just be a sign of sensitive hearing. 25 February 2012 | NewScientist | 17
IN BRIEF Honesty is always the best policy
Japan’s megaquake reactivated dormant faults The megaquake that shook the east coast of Japan in March 2011 reactivated dormant faults near Fukushima’s beleaguered nuclear reactors, geologists warn. “A strong quake may occur in the Futaba fault, only 5 to 6 kilometres away,” says Dapeng Zhao of Tohoku University. The fault runs parallel to the coast, right past both of Fukushima’s nuclear plants. Zhao’s team used data from more than 6000 quakes between June 2002 and October 2011 to make a 3D map of the crust in the area that suffered the largest aftershock recorded on land after the March megaquake:
a quake on 11 April in Iwiki. The images show fluid rising through the Pacific plate as it sinks under Japan. They say the March quake transferred stress to surrounding faults, causing them to adjust in aftershocks. The fluid in the Iwiki fault lubricated it, causing it to slip almost immediately in a large, magnitude 7 aftershock (Solid Earth, DOI: 10.5194/se-3-43-2012). Seismic readings from the Fukushima area reveal stresses and rising fluids similar to those found at Iwiki, so “the possibility of quake generation becomes much larger than before the 11 March quake”, says Zhao. A magnitude 7 quake would release far less energy than the magnitude 9 megaquake, but because the Futaba fault is so close to Fukushima, it would shake both power stations more strongly.
One-size-fits-all star clusters WHY do the universe’s oldest star clusters tend to be roughly the same size? The answer is grizzly. Globular star clusters are ancient, spherical blobs of stars. Most of these clusters are a few hundred thousand times the mass of our sun. The scarcity of much bigger clusters is no surprise as there must be an upper limit – but why are there so few small ones?
Using computer modelling, Diederik Kruijssen of the Max Planck Institute for Astrophysics in Garching, Germany, and his colleagues simulated the merger of two small galaxies. This process is thought to have been especially common in the early universe, when small structures were busy snowballing into larger ones. The collision compressed gas into dense knots, sparking star
formation and creating many new globular clusters. At the same time it seeded destruction, as the gravity of these knots disrupted clusters – both existing and new – passing nearby. Medium and large clusters survived, bound by their own strong gravity, but the smaller ones were ripped apart (arxiv.org/abs/1112.1065). All big galaxies probably formed in such mergers so this might be why globular clusters fall into such a narrow size range.
CHEATERS never prosper – at least not in the lab. A new finding contradicts the notion that cooperative organisms are vulnerable to freeloaders. Some bacteria send out signals that help a lab culture as a whole adapt to its environment, so other bugs ought to be able to benefit without wasting any of their own resources on signals. David Van Dyken at the University of British Columbia in Vancouver, Canada, studied the genetics of bacterial cultures and found this wasn’t true. Surprisingly, no known “cheating” genotype was common enough to suggest that it was an old-timer in the culture. Instead, cheaters are present simply because they arise through mutation faster than natural selection can purge them from the population. Cheating may not be a stable strategy (American Naturalist, DOI: 10.1086/664609).
Did early ungulate use echolocation? ONE of the first mammals to use echolocation may not have been a bat or a whale, but an early ancestor of horses. Hyopsodus was a weasel-like ungulate that lived 55 million years ago, around the time that bats evolved echolocation. Maéva Orliac of Montpellier University, France, and colleagues say that a new fossil cast of its braincase shows Hyopsodus had a large inferior colliculus, a brain region enlarged in echolocating animals (PLoS One, DOI: 10.1371/ journal.pone.0030000). They argue that Hyopsodus could echolocate, but Gregg Gunnell at Duke University in Durham, North Carolina, says the large inferior colliculus may just be a sign of sensitive hearing. 25 February 2012 | NewScientist | 17