Taiwan Earthquake: Tainan Hit By 6.4-Magnitude Quake

The death toll was rising in the historic city of Tainan, which bore the brunt of the 6.4-magnitude quake, as rescuers scoured rubble for survivors.

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Nearly 340 people were rescued from the rubble in Tainan, the city hit worst by the quake. About 2,000 firefighters and soldiers scrambled with ladders, cranes and other equipment to the ruins of the 17-floor residential building, which folded like an accordion onto its side after the quake struck.

Local authorities said Saturday night that more than 100 people remained missing and that rescuers were racing to find them. Taiwan’s official Central News Agency reported that 172 people were missing.

An entire residential complex of four buildings containing almost 100 homes toppled, left on its side with twisted metal girders exposed and clouds of dust rising from the jumbled concrete.

The official CNA news agency reported that the quake killed 14 people and injured 484 others, according to statistics by Taiwan’s rescue authorities. Most of the injured had been released from hospitals by Saturday night.

CNA said 153 people remained missing and that rescuers were racing to find them. Taiwan’s SETV reported that 101 adults and 41 children were missing. The number of missing was expected to drop because some of those listed might have been listed twice, hospitalized or not in the building at the time of the quake.

Rescuer Jian Zhengshun said the rescue work was difficult because part of the high-rise building was believed to be buried underground, with the quake loosening the earth. He said rescuers had to clear rubble for passages to reach people who were trapped.

Rescuers found the bodies of a 10-day-old infant, three other children and six adults at the collapsed building, the information center said. One other death was reported at the site, but details were not immediately available.

Authorities said two people were killed by falling objects elsewhere in Tainan.

Officials said four buildings collapsed in the quake which struck the island in the early hours of the morning, but rescue efforts are centring on the tower block that tumbled onto its side.

Firefighters pulled survivors from the twisted concrete, trying to access apartments through windows and scaling the rubble with ladders.

Around 800 troops have been mobilised to help the rescue effort, with sniffer dogs also searching through the rubble.

The baby, a man and a woman were pulled dead from the block, officials said, with 29 residents taken to hospital.

“These three people showed no signs of life before they were sent to the hospital,” said Lin Kuan-cheng, spokesman for the National Fire Agency.

“The search and rescue work continues there, home by home.”

Residents at the felled Wei-kuan Building told of their terror as the quake hit, with survivors pulled bleeding and crying from the ruins, some just in their underwear.

“I saw buildings shake up and down and left and right,” said one resident. “The first and second floor just collapsed,” he told local channel SET TV. Another man tied his clothes together to create a rope and lowered himself from his home on the ninth floor to the sixth floor below, Apple Daily reported.

One woman told how she had fought her way out of her home.

“I used a hammer to break the door of my home which was twisted and locked, and managed to climb out,” she told SET TV, weeping as she spoke.

Rescuers have freed more than 250 people from the apartment complex, with over 40 of them hospitalised.

Interior minister Chen Wei-jen said he feared there may be more people in the building than usual as family members would have returned to celebrate the Lunar New Year holidays next week.

“We are concerned that most members of those families may have returned for the coming new year holiday,” he said.

Heartfelt appeals for the missing were posted on social media. “My friend in Wei-kuan is currently missing. His brother is waiting at the scene and other relatives are at the hospital looking among those injured. If anyone has related news, please get in touch,” one user called applexgreen posted on Taiwan’s popular PTT forum.

Another named Ahan asked for information on a family of three with a two-year-old son who lived on the seventh floor of the building.

“My mother is the child’s nanny. We haven’t been able to get in contact,” the post said.

Officials were unable to give an estimate of how many were still trapped as they scoured the building.

As dawn broke, live Taiwanese TV showed survivors being brought gingerly from the building, including an elderly woman in a neck brace and others wrapped in blankets.

The trappings of daily life — a partially crushed air conditioner, pieces of a metal balcony, windows — lay twisted in what appeared to be nearby rubble.

People with their arms around firefighters were being helped from the building, and cranes were being used to search darkened parts of the structure for survivors.
One woman told how she had fought her way out of her home in one of the collapsed blocks.

“I used a hammer to break the door of my home which was twisted and locked, and managed to climb out,” she told local channel SET TV, weeping as she spoke.

Men in camouflage uniforms, apparently military personnel, marched into one area of collapse carrying large shovels.

Aerial images of at least two different buildings showed what appeared to be significant devastation. It was unclear if both were residential structures.

The Taiwanese news website ET Today reported a mother and a daughter were among the 34 people pulled from one of the Wei Guan buildings and that the girl drank her urine while waiting for rescue, which came sooner than expected.

The temblor struck about 4am local time. It was located some 36km southeast of Yujing, and struck about 10km underground, according to the US Geological Survey.

It was felt as a lengthy, rolling shake in the capital, Taipei, on the other side of the island. But Taipei was quiet, with no sense of emergency or obvious damage just before dawn.

Officials said there were 256 people registered as living in the complex, which contained 96 apartments.

Dazed and exhausted residents stood outside the toppled buildings, watching rescue workers free survivors — from infants to the elderly, some strapped to stretchers — and carefully hand them down ladders.

Cranes towered over the disaster zone with diggers trying to move slabs of concrete.

Eight shelters have been set up around the city, with over 100 people taking refuge there, while restaurants and hotels offered free food and rooms to residents.

“The buildings collapsed, but Tainan will stand again! Please treat here like your temporary home, rest well and freshen up. You aren’t alone,” said one Tainan hotel called Adagio Travel on its Facebook page.

Separately, at least 30 people were earlier freed from another residential seven-storey tower.

Officials said several blocks had collapsed or half collapsed in other parts of the city, with some buildings left leaning at alarming angles.

Across Tainan, more than 400 people were injured, with over 60 hospitalised. Around 400,000 had been left without water, authorities said, and more than 2,000 homes are still without electricity.

China has offered rescue assistance if needed, according to state news agency Xinhua.

The quake struck at a depth of 10 kilometres (six miles) at around 4:00am (2000 GMT Friday), 39 kilometres northeast of Kaohsiung, Taiwan’s second-largest city.
Taiwan lies near the junction of two tectonic plates and is regularly hit by earthquakes.

The Pacific Tsunami Warning Center said a destructive Pacific-wide tsunami was not expected.

A strong 6.3-magnitude quake which hit central Taiwan in June 2013 killed four people and caused widespread landslides.

A 7.6-magnitude quake struck the island in September 1999 and killed around 2400 people.

Galactic Center’s Gamma Rays Unlikely To Originate From Dark Matter, Evidence Shows

Bursts of gamma rays from the center of our galaxy are not likely to be signals of dark matter but rather other astrophysical phenomena such as fast-rotating stars called millisecond pulsars, according to two new studies, one from a team based at Princeton University and the Massachusetts Institute of Technology and another based in the Netherlands.

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Previous studies suggested that gamma rays coming from the dense region of space in the inner Milky Way galaxy could be caused when invisible dark matter particles collide. But using new statistical analysis methods, the two research teams independently found that the gamma ray signals are uncharacteristic of those expected from dark matter. Both teams reported the finding in the journal Physical Review Letters this week.

“Our analysis suggests that what we are seeing is evidence for a new astrophysical source of gamma rays at the center of the galaxy,” said Mariangela Lisanti, an assistant professor of physics at Princeton. “This is a very complicated region of the sky and there are other astrophysical signals that could be confused with dark matter signals.”

The center of the Milky Way galaxy is thought to contain dark matter because it is home to a dense concentration of mass, including dense clusters of stars and a black hole. A conclusive finding of dark matter collisions in the galactic center would be a major step forward in confirming our understanding of our universe. “Finding direct evidence for these collisions would be interesting because it would help us understand the relationship between dark matter and ordinary matter,” said Benjamin Safdi, a postdoctoral researcher at MIT who earned his Ph.D. in 2014 at Princeton.

To tell whether the signals were from dark matter versus other sources, the Princeton/MIT research team turned to image-processing techniques. They looked at what the gamma rays should look like if they indeed come from the collision of hypothesized dark matter particles known as weakly interacting massive particles, or WIMPs. For the analysis, Lisanti, Safdi and Samuel Lee, a former postdoctoral research fellow at Princeton who is now at the Broad Institute, along with colleagues Wei Xue and Tracy Slatyer at MIT, studied images of gamma rays captured by NASA’s Fermi Gamma-ray Space Telescope, which has been mapping the rays since 2008.

Dark matter particles are thought to make up about 85 percent of the mass in the universe but have never been directly detected. The collision of two WIMPs, according to a widely accepted model of dark matter, causes them to annihilate each other to produce gamma rays, which are the highest-energy form of light in the universe.

According to this model, the high-energy particles of light, or photons, should be smoothly distributed among the pixels in the images captured by the Fermi telescope. In contrast, other sources, such as rotating stars known as pulsars, release bursts of light that show up as isolated, bright pixels.

The researchers applied their statistical analysis method to images collected by the Fermi telescope and found that the distribution of photons was clumpy rather than smooth, indicating that the gamma rays were unlikely to be caused by dark matter particle collisions.

Exactly what these new sources are is unknown, Lisanti said, but one possibility is that they are very old, rapidly rotating stars known as millisecond pulsars. She said it would be possible to explore the source of the gamma rays using other types of sky surveys involving telescopes that detect radio frequencies.

Douglas Finkbeiner, a professor of astronomy and physics at Harvard University who was not directly involved in the current study, said that although the finding complicates the search for dark matter, it leads to other areas of discovery. “Our job as astrophysicists is to characterize what we see in the universe, not get some predetermined, wished-for outcome. Of course it would be great to find dark matter, but just figuring out what is going on and making new discoveries is very exciting.”

According to Christoph Weniger from the University of Amsterdam and lead author of the Netherlands-based study, the finding is a win-win situation: “Either we find hundreds or thousands of millisecond pulsars in the upcoming decade, shedding light on the history of the Milky Way, or we find nothing. In the latter case, a dark matter explanation for the gamma ray excess will become much more obvious.”

Research May Explain Mysterious Deep Earthquakes In Subduction Zones

Geologists from Brown University may have finally explained what triggers certain earthquakes that occur deep beneath the Earth’s surface in subduction zones, regions where one tectonic plate slides beneath another.

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Subduction zones are some of the most seismically active areas on earth. Earthquakes in these spots that occur close to the surface can be devastating, like the one that struck Japan in 2011 triggering the Fukushima nuclear disaster. But quakes also occur commonly in the subducting crust as it pushes deep below the surface — at depths between 70 and 300 kilometers. These quakes, known as intermediate depth earthquakes, tend to be less damaging, but can still rattle buildings.

Intermediate depth quakes have long been something of a mystery to geologists.

“They’re enigmatic because the pressures are so high at that depth that the normal process of frictional sliding associated with earthquakes is inhibited,” said Greg Hirth, professor of earth, environmental, and planetary sciences at Brown. “The forces required to get things to slip just aren’t there.”

But through a series of lab experiments, Hirth and postdoctoral researcher Keishi Okazaki have shown that as water escapes from a mineral called lawsonite at high temperatures and pressures, the mineral becomes prone to the kind of brittle failure required to trigger an earthquake.

“Keishi’s experiments were basically the first tests at conditions appropriate for where these earthquakes actually happen in the earth,” Hirth said. “They’re really the first to show strong evidence for this dehydration embrittlement.”

The work will be published on February 4, 2016 in the journal Nature.

The experiments were done in what’s known as a Grigg’s apparatus. Okazaki placed samples of lawsonite in a cylinder and heated it up through the range of temperatures where water becomes unstable in lawsonite at high pressures. A piston then increased the pressure until the mineral began to deform. A tiny seismometer fixed to the apparatus detected sudden cracking in the lawsonite, a signal consistent with brittle failure.

Okazaki performed similar experiments using a different mineral, antigorite, which had been previously implicated as contributing to intermediate depth seismicity. In contrast to lawsonite, the antigorite failed more gradually — squishing rather than cracking — suggesting that antigorite does not play a role in these quakes.

“That’s one of the cool things about this,” Hirth said. “For 50 years everyone has assumed this is a process related to antigorite, despite the fact that there wasn’t much evidence for it. Now we have good experimental evidence of this dehydration process involving lawsonite.”

If lawsonite is indeed responsible for intermediate depth earthquakes, it would explain why such quakes are common in some subduction zones and not others. The formation of lawsonite requires high pressures and low temperatures. It is found in so-called “cold” subduction zones in which the suducting crust is older and therefore cooler in temperature. One such cold zone is found in northwest Japan. But conditions in “hot” subduction zones, like the Cascadia subduction zone off the coast of Washington state, aren’t conducive to the formation of lawsonite.

“In hot subduction zones, we have very few earthquakes in the subducting crust because we have no lawsonite,” Okazaki said. “But in cold subduction zones, we have lawsonite and we get these earthquakes.”

Ultimately, Hirth says research like this might help scientists to better understand why earthquakes happen at different places under different conditions.

“Trying to put into the context of all earthquakes how these processes are working might be important not just for understanding these strange types of earthquakes, but all earthquakes,” he said. “We don’t really understand a lot of the earthquake cycle. Predictability is the ultimate goal, but we’re still at the stage of thinking about what’s the recipe for different kinds of earthquakes. This appears to be one of those recipes.”

In The Southern Ocean, A Carbon-Dioxide Mystery Comes Clear

Twenty thousand years ago, when humans were still nomadic hunters and gatherers, low concentrations of carbon dioxide in the atmosphere allowed the earth to fall into the grip of an ice age. But despite decades of research, the reasons why levels of the greenhouse gas were so low then have been difficult to piece together.

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New research, published today in the leading journal Nature, shows that a big part of the answer lies at the bottom of the world. Sediment samples from the seafloor, more than 3 kilometers beneath the ocean surface near Antarctica, support a long-standing hypothesis that more carbon dioxide was dissolved in the deep Southern Ocean at times when levels in the atmosphere were low.

Among other things, the study shows that during the ice age, the deep Southern Ocean carried much smaller amounts of oxygen than today. This indicates that photosynthetic algae, or phytoplankton, were taking up large amounts of carbon dioxide near the surface. As dead algae sank to the depths, they were consumed by other microbes, which used up the oxygen there in the process. The scientists found chemical fingerprints of the oxygen level by measuring trace metals in the sediments.

The evidence “is a long-sought smoking gun that there was increased deep ocean carbon storage when the atmospheric CO2 was lower,” said Sam Jaccard of the University of Bern, Switzerland, the study’s lead author.

Coauthor Robert Anderson, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory, said the study “finally provides the long-sought direct evidence that extra carbon was trapped in the deep sea by the buildup of decaying organic matter from above.” He added, “It’s also clear that the buildup and release of CO2 stored in the deep ocean during the ice age was driven by what was happening in the ocean around Antarctica.”

The study also shows that variations in carbon-dioxide storage in the Southern Ocean were probably behind a series of natural “wobbles” in atmospheric levels of about 20 parts per million that took place over thousands of years. The study suggests that the wobbles were probably caused by changes in the amount of iron-rich dust, which fertilizes phytoplankton, being blown from land onto the ocean surface. Levels may also have been influenced by varying amounts of carbon being released from the deep ocean as ocean currents changed, said the authors.

The study may hold powerful lessons for today. While the natural 20-part-per million wobbles took thousands of years to happen, carbon dioxide levels have risen that much in just the last nine years, due to human emissions. Levels are now about 400 parts per million, versus about 280 in the early 1800s. “The current rate of emissions is just so fast compared to the natural variations that it’s hard to compare,” said study coauthor Eric Galbraith of the Autonomous University of Barcelona. “We are entering climate territory for which we don’t have a good geological analog.”

Turbulent Times: When Stars Approach

HITS astrophysicists use new methods to simulate the common-envelope phase of binary stars, discovering dynamic irregularities that may help to explain how supernovae evolve.

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When we look at the night sky, we see stars as tiny points of light eking out a solitary existence at immense distances from Earth. But appearances are deceptive. More than half the stars we know of have a companion, a second nearby star that can have a major impact on their primary companions. The interplay within these so-called binary star systems is particularly intensive when the two stars involved are going through a phase in which they are surrounded by a common envelope consisting of hydrogen and helium. Compared to the overall time taken by stars to evolve, this phase is extremely short, so astronomers have great difficulty observing and hence understanding it. This is where theoretical models with highly compute-intensive simulations come in. Research into this phenomenon is relevant understanding a number of stellar events such as supernovae.

Using new methods, astrophysicists Sebastian Ohlmann, Friedrich Röpke, Rüdiger Pakmor, and Volker Springel of the Heidelberg Institute for Theoretical Studies (HITS) have now made a step forward in modeling this phenomenon. As they report in The Astrophysical Journal Letters, the scientists have successfully used simulations to discover dynamic irregularities that occur during the common-envelope phase and are crucial for the subsequent existence of binary star systems. These so-called instabilities change the flow of matter inside the envelope, thus influencing the stars’ distance from one another and determining, for example, whether a supernova will ensue and, if so, what kind it will be.

The article is the fruit of collaboration between two HITS research groups, the Physics of Stellar Objects (PSO) group and the Theoretical Astrophysics group (TAP). Prof. Volker Springel’s Arepo code for hydrodynamic simulations was used and adapted for the modeling. It solves the equations on a moving mesh that follows the mass flow, and thus enhances the accuracy of the model.

Two stars, one envelope

More than half the stars we know of have evolved in binary star systems. The energy for their luminosity comes from the nuclear fusion of hydrogen at the core of the stars. As soon as the hydrogen fueling the nuclear fusion is exhausted in the heavier of the two stars, the star core shrinks. At the same time, a highly extended stellar envelope evolves, consisting of hydrogen and helium. The star becomes a red giant.

As the envelope of the red giant goes on expanding, the companion star draws the envelope to itself via gravity, and part of the envelope flows towards it. In the course of this process the two stars come closer to one another. Finally, the companion star may fall into the envelope of the red giant and both stars are then surrounded by a common envelope. As the core of the red giant and the companion draw closer together, the gravity between them releases energy that passes into the common envelope. As a result, the envelope is ejected and mixes with interstellar matter in the galaxy, leaving behind it a close binary star system consisting of the core of the giant and the companion star.

The path to stellar explosion

Sebastian Ohlmann of the PSO group explains why this common-envelope phase is important for our understanding of the way various star systems evolve: “Depending on what the system of the common envelope looks like initially, very different phenomena may ensue in the aftermath, such as thermonuclear supernovae.” Ohlmann and colleagues are investigating the run-up to these stellar explosions, which are among the most luminous events in the universe and can light up a whole galaxy. But modeling the systems that can lead to such explosions is bedeviled by major uncertainty in the description of the common-envelope phase. One of the reasons for this is that the core of the giant is anything between a thousand and ten thousand times smaller than the envelope, so that spatial and temporal scale differences complicate the modeling process and make approximations necessary. The methodically innovative simulations performed by the Heidelberg scientists are a first step towards a better understanding of this phase.

Been Here Before: How The Brain Builds Place Memories

Tübingen neuroscientists have succeeded in activating dormant memory cells in rats. Using weak electrical impulses targeted at previously inactive cells in the hippocampus, the researchers induced the cells to recognize the exact place where the impulse had been first administered. In rodents as well as humans, the hippocampus is the brain area responsible for memory. Therefore, the new study by researchers of the Werner Reichardt Centre for Integrative Neuroscience (CIN) at the University of Tübingen offers insight into the question of how memories are formed within our brains. Their findings are published in Current Biology.

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Memory is one of the most important functions of our brain. Not only does it allow us to regale our grandchildren with the exploits of our youth; it is essential for many everyday procedures. Our memory is constantly and immediately active whenever we experience a new thing. For instance, after meeting somebody only once, we still recognise them after hours or days. And even when we go somewhere for the first time — for instance, the perfume section of a department store, a particular office in a building, or the toilet in a restaurant — we will usually be able to find our way to the exit without a problem.

So our memory is not only constantly alert, it also constructs new recollections very quickly — often during the first interaction. The reason for this alacrity of memory formation is the fact that for every person, every place — and probably a lot of other concepts, too — there are individual memory cells that are specifically assigned to that memory. One subtype of these neurons called granule cells is situated in the hippocampus, a centrally located brain area. Whenever memory concepts like “my living room” or “Angela Merkel” are activated — e.g. by stepping into the living room or by seeing a photo of the German chancellor — the small number of granule cells associated with that memory become activated in the form of electrical discharges. The large majority of the remaining neurons, however, remain dormant.

Up to now, the mechanisms through which individual granule cells are assigned to specific memories were not understood. The question of whether ‘silent’ granule cells can become activated under certain circumstances proved particularly intriguing. The Tübingen research team led by Dr. Andrea Burgalossi worked on the assumption that granule cells which receive electrical impulses can be ‘un-silenced’ and thus become memory cells. To confirm their hypothesis, they inserted hair-thin microelectrodes into the dentate gyrus of rats — an area within the hippocampus which is responsible for memories of space and location — allowing them to send weak electrical impulses to individual granule cells.

The rats were allowed to explore a simple labyrinth, and at a specific location within this labyrinth, individual granule cells were stimulated with weak electrical pulses (in the nanoampere range) via the microelectrode. The same electrode allowed the researchers to measure the subsequent activity of the stimulated cells. The result: whenever the rats arrived at the same spot within the labyrinth where the original impulse had been administered, stimulated granule cells now fired spontaneously. The electrical impulse had thus induced the individual granule cells to form a place memory.

Moreover, Dr. Burgalossi and his team found that the duration and temporal pattern of the impulses administered play a large role. The impulses formed more durable place memories when they followed the natural theta-rhythm of the brain — a periodic increase and decrease in electrical potential which takes place roughly 4 to 12 times per second. Another finding could turn out to be of equal importance: rats that were new to the labyrinth reacted much more keenly to the induced place memory than rats that had been given the run of the labyrinth beforehand. Apparently, memory cells can be activated more easily when the brain is exposed to novel information.

These new insights into memory formation shed light on one of the most important functions of the human brain. And though there is still much to do before fundamental findings like these can offer new strategies for the treatment of brain diseases which affect memory formation (e.g. Alzheimer’s disease, Parkinson, dementia), they represent an indispensable first step on the way.

UPDATE :Can Slow Creep Along Thrust Faults Help Forecast Megaquakes?

In Japan and areas like the Pacific Northwest where megathrust earthquakes are common, scientists may be able to better forecast large quakes based on periodic increases and decreases in the rate of slow, quiet slipping along the fault.

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This hope comes from a new study by Japanese and UC Berkeley seismologists, looking at the more than 1,000-kilimeter-long fault off northeast Japan where the devastating 2011 Tohoku-oki earthquake originated, generating a tsunami that killed thousands. There, the Pacific Plate is trundling under the Japan plate, not only causing megaquakes like the magnitude 9 in 2011, but giving rise to a chain of Japanese volcanoes.

The scientists studied 28 years of earthquake measurements, looking at quakes of magnitude 2.5 or greater between 1984 and 2011. They discovered 1,515 locations off the coast of Japan where small repeating earthquakes happen — 6,126 quakes in all.

According to co-author Robert Nadeau, a UC Berkeley seismologist and a fellow with the Berkeley Institute for Data Science (BIDS), an analysis of these quakes found that larger, more destructive earthquakes — those of magnitude 5 or greater — occurred much more frequently when the periodic slow-slip was fastest. This included the great Tohoku-oki earthquake, which also devastated a nuclear power plant and led to widespread radioactive contamination.

“The persistence of the periodic pattern over time may help us refine earthquake probabilities in the future by taking into account the times of expected slow-slip pulses,” he said. “Right now, seismologists gives forecasts on a 30-year time frame and assume nothing is changing on a shorter time scale. Our study points out that things are changing, and in a periodic way. So it may be possible for scientists to give shorter time ranges of greater and lower probability for larger events to happen.”

The research was led by Naoki Uchida, a seismologist at Tohoku University, and included UC Berkeley seismologist Roland Burgmann, professor of earth and planetary science. They published their findings in the Jan. 29 issue of Science.

Slip, Nadeau said, is the relative motion between two sides of a fault, sometimes but not always resulting in ground shaking. So-called slow-slip or creep is what scientists call “fault slip,” which happens quietly, without generating shaking, not even microquakes or faint tremors.

Regions of a fault that slip quietly are considered to be weak or un-coupled. But within these un-coupled regions of rock underground there are variously-sized patches of fault that are much stronger, or coupled. These patches resist the quiet slip happening around them, only slipping when the pushing and pulling from the surrounding quiet slip stresses them to their breaking point and they “snap” in an earthquake.

“There is a relationship, which we showed here in California, between the time between ‘snaps’ on the small, strong patches where earthquakes happen and how much slip took place on the quiet fault surrounding them,” Nadeau said. “Using this relationship for thousands of repeating earthquakes in Japan, we were able to map out the evolution of slow-slip on the megathrust. Then, by studying the pattern of this evolution, we discovered the periodic nature of the megathrust slow-slip and its relationship to larger earthquakes.”

Nadeau and the late UC Berkeley seismologist Thomas McEvilly showed 12 years ago that periodic slow slip occurred all along the San Andreas Fault, from Parkfield to Loma Prieta, Calif. In 2009 the group also observed deeper, transient and periodic slow-slip on the San Andreas — this time associated with faint shaking called tremor — and that it was linked with two larger quakes occurring in 2003 and 2004 at San Simeon and Parkfield, Calif. respectively.

“The phenomenon we found in Japan may not be limited to megathrust zones,” he said. “Our 2004 study, more limited in scope than this one, showed a similar periodic slip process and an association between larger quakes — those of magnitude 3.5 or greater — and repeating earthquakes along the 170 km stretch of San Andreas Fault that we studied.”