New report says Silicon Valley faults could set off global tremors

By Monte Morin, Los Angeles Times

Planet Earth may be 4.5 billion years old, but that doesn’t mean it can’t serve up a shattering surprise now and again.

Such was the case on April 11 when two massive earthquakes erupted beneath the Indian Ocean off the coast of the Indonesian island of Sumatra, far from the usual danger zones. Now scientists say the seafloor ruptures are part of a long suspected, yet never before observed, event: the slow-motion splitting of a vast tectonic plate.

The first of the quakes, a magnitude 8.7, was 20 times more powerful than California’s long anticipated “big one” and tore a complex network of faults deep in the ocean floor. The violence also triggered unusually large aftershocks thousands of miles away, including four off North America’s western coast.

“It was jaw-dropping,” said Thorne Lay, a professor of Earth and planetary sciences at UC Santa Cruz. “It was like nothing we’d ever seen.”

At first, Lay wondered whether the computer code he used to analyze earthquakes was wrong. Eventually, he and other scientists realized that they had documented the breakup of the Indo-Australian plate into two pieces, an epic process that began roughly 50 million years ago and will continue for tens of millions more. Lay and other scientists reported their findings online Wednesday in the journal Nature.

Most great earthquakes occur along plate borders, where one plate dives beneath the adjoining plate and sinks deep into Earth’s mantle, a process called subduction. The April 11 quakes, however, occurred in the middle of the plate and involved a number of strike-slip faults, meaning the ground on one side of the fault moves horizontally past ground on the other side.

Scientists say the 8.7 main shock broke four faults. The quake lasted 2 minutes and 40 seconds — most last just seconds — and was followed by a second main shock, of magnitude 8.2, two hours later.

Unlike the magnitude 9.1 temblor that struck in the same region on Dec. 26, 2004, and created a deadly tsunami, the April 11 quakes did not cause similar destruction. That’s because horizontally moving strike-slip faults do not induce the massive, vertical displacement of water that thrust faults do on the borders of plates.

The type of interplate faults involved in the Sumatran quakes are the result of monumental forces, some of which drove the land mass of India into Asia millions of years ago and lifted the Himalayan Mountains. As the Indo-Australian plate continues to slide northwest, the western portion of the plate, where India is, has been grinding against and underneath Asia. But the eastern portion of the plate, which contains Australia, keeps on moving without the same obstruction. That difference creates squeezing pressure in the area where the quakes occurred.

The study authors say that over time, as more quakes occur and new ruptures appear, the cracks will eventually coalesce into a single fissure.

“This is part of the messy business of breaking up a plate,” said University of Utah seismologist Keith Koper, senior author of one of the studies. “Most likely it will take thousands of similar large quakes for that to happen.”

The quakes were also notable for triggering powerful aftershocks thousands of miles away. Though major quakes have been known to trigger aftershocks at great distance, they are usually less than 5.5 in magnitude. The April earthquakes triggered 11 aftershocks that measured 5.5 or greater in the six days that followed, including a magnitude 7. Remote shocks were felt 6,000 to 12,000 miles from the main quakes.

Fred Pollitz, a geophysicist with the U.S. Geological Survey in Menlo Park, Calif., and lead author of one of the studies, said the quakes were extremely effective in transmitting seismic wave radiation around the world. Though Pollitz said the magnitude of the larger Sumatran quake is No. 10 on the list of quakes since 1900, no other temblor has triggered so many strong aftershocks so far away.

“It’s the most powerful earthquake ever in terms of capability of putting stress on other fault zones around the world,” he said.

Pollitz said the quakes were likely to teach seismologists about the physics of earthquakes, particularly those along strike-slip faults. That knowledge, he said, would certainly apply to California’s San Andreas fault, which is also a strike-slip fault.

Lay said that the Sumatran quakes were most surprising in that they were completely unanticipated by seismologists and that he did not expect the event to repeat any time soon.

monte.morin@latimes.com

Big quake was part of crustal plate breakup

by Staff Writers
Salt Lake City UT (SPX)

This map of the Indian Ocean region shows boundaries of Earth’s tectonic plates in the area, and the epicenters (red stars) of two great earthquakes that happened April 11, 2012. A new study from the University of Utah and University of California, Santa Cruz, says the main shock measured 8.7 in magnitude, about 40 times larger than the previous estimate of 8.6. An 8.2-magnitude quake followed two hours later.The scientists explain how at least four faults ruptured during the 8.7 main shock, and how both great quakes are likely part of the breakup of the Indo-Australian Plate into separate subplates. The northeastward-moving plate is breaking up over scores of millions of years because the western part of the plate is bumping into Asia and slowing down, while the eastern part is sliding more easily beneath Sumatra and the Sunda plate. Credit: Keith Koper, University of Utah Seismograph Stations.

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Taiwan on Thursday issued a warning over a strong typhoon approaching the island which could bring torrential rains and trigger landslides, a month after another heavy storm left six dead.

Residents in the north and east of the island were asked to take precautions against Typhoon Jelawat which is gaining momentum and approaching the island, the Central Weather Bureau said in a statement.

As of 0900 GMT, Jelawat was 380 kilometres (236 miles) southeast of the island’s southern-most tip.

With a radius of 250 kilometres and packing winds of up to 191 kilometres an hour, the typhoon was moving north-northwest at 14 kilometres per hour.

Typhoon Saola pounded Taiwan with fierce winds and torrential rain in August that left six people dead and forced nearly the entire island to shut down.

Britain’s most severe September storms for 30 years flooded homes and businesses in the historic city of York on Thursday and threatened chaos for much of northern England.

Residents took to boats to navigate the picturesque streets of the city dating from Roman times but officials said flood defences would cope as the River Ouse reached near record levels, three metres (10 feet) higher than normal.

City of York Council insisted the centre was “very much open for business” despite 80 properties being flooded while defences in the nearby village of Cawood were bolstered overnight by 4,000 sandbags.

“Loads of staff have been working through the night to protect the city,” said Sally Burns from the council, who said experts believed the river levels had peaked.

“We need to be careful and make sure we are giving (sandbags) to the people who are a priority, we can see on the monitors where the problems are.”

The Met Office issued more than 50 flood warnings — indicating flooding is expected — and 80 flood alerts – meaning flooding is possible — in England and Wales.

Further rain was forecast for Thursday, putting thousands of home in northern England at risk.

In Newburn, northeast England, a four-storey block of flats teetered on the brink of collapse after floodwaters destroyed its foundations.

Police arrested a man and a woman in connection with the looting of �20,000 ($32,300, 25,000 euros) worth of bicycles from a nearby shop.

Elsewhere, police were investigating the discovery of two bodies on the banks of the swollen River Clywedog in north Wales.

The body of a 27-year-old woman was found on Wednesday and the second body, believed to be male, was discovered on Thursday. Police believe they are linked.

An 11-year-old boy was fighting for his life after being struck by lightning in storms in Swindon, southwest England.

The storms have been caused by an unusually deep area of low pressure but conditions are expected to improve over the next 24 hours.

Global grain production is expected to reach a record high of 2.4 billion tons in 2012, an increase of 1 percent from 2011 levels, according to new research conducted by the Worldwatch Institute’s Nourishing the Planet project (www.worldwatch.org) for the Institute’s Vital Signs Online service.

According to the United Nations Food and Agriculture Organization (FAO), the production of grain for animal feed is growing the fastest – a 2.1 percent increase from 2011. Grain for direct human consumption grew 1.1 percent from 2011, write report authors Danielle Nierenberg and Katie Spoden.

In 2011, the amount of grain used for food totaled 571 million tons, with India consuming 89 million tons, China 87 million tons, and the United States 28 million tons, according to the International Grains Council.

The world relies heavily on wheat, maize (corn), and rice for daily sustenance: of the 50,000 edible plants in the world, these three grains account for two-thirds of global food energy intake. Grains provide the majority of calories in diets worldwide, ranging from a 23 percent share in the United States to 60 percent in Asia and 62 percent in North Africa.

Maize production in the United States – the largest producer – was expected to reach a record 345 million tons in 2012; however, drought in the Great Plains has altered this estimate severely. Maize yields for the 2012-13 growing season are now expected to decrease 13 percent from 2011 production, for a total production of 274.3 million tons.

The reliance on grain crops for food security is threatened by more-extreme climatic events, especially droughts and floods. According to the United Nations International Strategy for Disaster Risk Reduction, the World Food Programme, and Oxfam International, some 375 million people will be affected by climate change-related disasters by 2015.

By 2050, the FAO notes, 10-20 percent more people will be subject to hunger based on the changing climate’s effects on agriculture, and 24 million more children are expected to be malnourished – 21 percent more than if there were no climate change.

“The relationship between food security, grain production, and climate change is especially important in 2012,” said Nierenberg, a Worldwatch senior researcher and Nourishing the Planet project director.

“The recent drought affecting the United States and the rest of the world show the need to reduce price volatility, move away from fossil fuel-based agriculture, and recognize the importance of women farmers to increase resilience to climate change.”

The drought taking place in the Midwest and Great Plains of the United States is considered the country’s worst in 50 years, coming close to matching the late-1930s Dust Bowl.

The drought is expected to cost many billions of dollars and could top the list as one of the most expensive weather-related disasters in U.S. history. The global market will be most affected by this drought, as so much of the developing world relies on U.S. corn and soybean production.

Food prices have already begun to increase due to lower yields, and price fluctuations will inevitably affect food security around the globe.

Further highlights from the report:

+ The FAO expects global maize production to increase 4.1 percent from 2011, reaching an estimated 916 million tons in 2012.

+ Global rice production achieved an all-time high of 480 million tons in 2011, a 2.6 percent increase from 2010.

+ World wheat production is projected to drop to 675.1 million tons in 2012, down 3.6 percent from 2011, with the largest declines in feed and biofuel utilization.

+ Since 1961, grain production has increased 269 percent and grain yield has increased 157 percent, while the grain harvest area has increased only 25 percent.

+ This is due largely to the Green Revolution and the introduction of high-yielding grain varieties.

High biodiversity acts as an insurance policy for nature and society alike as it increases the likelihood that at least some species will be sufficiently resilient to sustain important functions such as water purification and crop pollination in a changing environment.

“It’s the same principle as an investment portfolio – you’d be mad to put all your eggs in one basket,” says researcher Johan Eklof.

Experiments with eelgrass meadows in shallow inlets on the west coast of Sweden are now showing that climate change can exacerbate the negative effects of losing sensitive species, and that the insurance effect of biodiversity may be weaker than what we typically assume.

Eelgrass meadows in shallow inlets are important nursery habitats for cod, for example. Since the early 1980s the prevalence of eelgrass has fallen dramatically along the Bohuslan coast.

This is thought to be due partly to eutrophication, which favours mats of filamentous “nuisance” algae which shade and suffocate the eelgrass, and partly to the loss of cod, which has resulted in a huge increase in numbers of smaller predatory fish.

These predatory fish, in turn, reduce numbers of Grammarus locusta, herbivorous crustaceans which are effective grazers that normally control the filamentous algae.

This type of cascade effect has become increasingly common both onshore and off as many types of predator have been wiped out by hunting or fishing. Worryingly, theory and observations would indicate that these effects could magnify the effects of global warming, which favours heat-tolerant but grazing-sensitive plants such as filamentous algae.

At the Sven Loven Centre for Marine Sciences’ Kristineberg research station on Gullmarsfjorden, researchers from the University of Gothenburg’s Department of Biology and Environmental Sciences have developed miniature ecosystems in outdoor aquariums and have been investigating how future ocean warming and ocean acidification could affect the balance between eelgrass and filamentous algae.

The effects were unexpectedly clear and unambiguous: it was the diversity of algal herbivores that determined the extent to which the ecosystem was affected by warming and acidification.

“High diversity meant that neither warming nor acidification had any real effect as the algae were eaten before they managed to grow and shade the eelgrass,” says researcher and biologist Johan Eklof, who headed up the study.

“But when we simultaneously simulated the effects of fishing and removed the effective but vulnerable herbivor Grammarus locusta, the algae took over the ecosystem – especially in the warmer conditions.”

The researchers believe that we should be concerned about the results.

“Most management is based on the assumption that we afford to lose the most sensitive species because other, more resilient species will take their place,” says Johan Eklof. “But this may not be the case with future climate changes, as it can reduce the net efficiency of the resilient species – without directly affecting them.”

However, the researchers are also careful to point out that there is still hope if society does decide to take action.

“If we protect the local biodiversity we still have, and restore the diversity we’ve lost, by for example protecting predatory fish stocks in coastal areas and reducing nutrient loading, then we’ll probably be able to increase the ecosystems’ resilience to climate change.”