Tag Archives: earth sciences

Can we predict earthquakes?

BBC News – Can we predict when and where quakes will strike?.

l'Aquila earthquake Seismologists try to manage the risk of building damage and loss of life

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This week, six seismologists go on trial for the manslaughter of 309 people, who died as a result of the 2009 earthquake in l’Aquila, Italy.

The prosecution holds that the scientists should have advised the population of l’Aquila of the impending earthquake risk.

But is it possible to pinpoint the time and location of an earthquake with enough accuracy to guide an effective evacuation?

There are continuing calls for seismologists to predict where and when a large earthquake will occur, to allow complete evacuation of threatened areas.

What causes an earthquake?

An earthquake is caused when rocks in the Earth’s crust fracture suddenly, releasing energy in the form of shaking and rolling, radiating out from the epicentre.

The rocks are put under stress mostly by friction during the slow, 1-10 cm per year shuffling of tectonic plates.

The release of this friction can happen at any time, either through small frequent fractures, or rarer breaks that release a lot more energy, causing larger earthquakes.

It is these large earthquakes that have devastating consequences when they strike in heavily populated areas.

Attempts to limit the destruction of buildings and the loss of life mostly focus on preventative measures and well-communicated emergency plans.

Predicting an earthquake with this level of precision is extremely difficult, because of the variation in geology and other factors that are unique to each location.

Attempts have been made, however, to look for signals that indicate a large earthquake is about to happen, with variable success.

Historically, animals have been thought to be able to sense impending earthquakes.

Noticeably erratic behaviour of pets, and mass movement of wild animals like rats, snakes and toads have been observed prior to several large earthquakes in the past.

Following the l’Aquila quake, researchers published a study in the Journal of Zoology documenting the unusual movement of toads away from their breeding colony.

But scientists have been unable to use this anecdotal evidence to predict events.

The behaviour of animals is affected by too many factors, including hunger, territory and weather, and so their erratic movements can only be attributed to earthquakes in hindsight.

Precursor events

When a large amount of stress is built up in the Earth’s crust, it will mostly be released in a single large earthquake, but some smaller-scale cracking in the build-up to the break will result in precursor earthquakes.

Start Quote

There is no scientific basis for making a prediction”

Richard Walker University of Oxford

These small quakes precede around half of all large earthquakes, and can continue for days to months before the big break.

Some scientists have even gone so far as to try to predict the location of the large earthquake by mapping the small tremors.

The “Mogi Doughnut Hypothesis” suggests that a circular pattern of small precursor quakes will precede a large earthquake emanating from the centre of that circle.

While half of the large earthquakes have precursor tremors, only around 5% of small earthquakes are associated with a large quake.

So even if small tremors are felt, this cannot be a reliable prediction that a large, devastating earthquake will follow.

“There is no scientific basis for making a prediction”, said Dr Richard Walker of the University of Oxford.

In several cases, increased levels of radon gas have been observed in association with rock cracking that causes earthquakes.

Leaning building Small ground movements sometimes precede a large quake

Radon is a natural and relatively harmless gas in the Earth’s crust that is released to dissolve into groundwater when the rock breaks.

Similarly, when rock cracks, it can create new spaces in the crust, into which groundwater can flow.

Measurements of groundwater levels around earthquake-prone areas see sudden changes in the level of the water table as a result of this invisible cracking.

Unfortunately for earthquake prediction, both the radon emissions and water level changes can occur before, during, or after an earthquake, or not at all, depending on the particular stresses a rock is put under.

Advance warning systems

The minute changes in the movement, tilt, and the water, gas and chemical content of the ground associated with earthquake activity can be monitored on a long term scale.

Measuring devices have been integrated into early warning systems that can trigger an alarm when a certain amount of activity is recorded.

Start Quote

Prediction will only become possible with a detailed knowledge of the earthquake process. Even then, it may still be impossible”

Dr Dan Faulkner University of Liverpool

Such early warning systems have been installed in Japan, Mexico and Taiwan, where the population density and high earthquake risk pose a huge threat to people’s lives.

But because of the nature of all of these precursor reactions, the systems may only be able to provide up to 30 seconds’ advance warning.

“In the history of earthquake study, only one prediction has been successful”, explains Dr Walker.

The magnitude 7.3 earthquake in 1975 in Haicheng, North China was predicted one day before it struck, allowing authorities to order evacuation of the city, saving many lives.

But the pattern of seismic activity that this prediction was based on has not resulted in a large earthquake since, and just a year later in 1976 a completely unanticipated magnitude 7.8 earthquake struck nearby Tangshan causing the death of over a quarter of a million people.

The “prediction” of the Haicheng quake was therefore just a lucky unrepeatable coincidence.

A major problem in the prediction of earthquake events that will require evacuation is the threat of issuing false alarms.

Scientists could warn of a large earthquake every time a potential precursor event is observed, however this would result in huge numbers of false alarms which put a strain on public resources and might ultimately reduce the public’s trust in scientists.

“Earthquakes are complex natural processes with thousands of interacting factors, which makes accurate prediction of them virtually impossible,” said Dr Walker.

Seismologists agree that the best way to limit the damage and loss of life resulting from a large earthquake is to predict and manage the longer-term risks in an earthquake-prone area. These include the likelihood of building collapsing and implementing emergency plans.

“Detailed scientific research has told us that each earthquake displays almost unique characteristics, preceded by foreshocks or small tremors, whereas others occur without warning. There simply are no rules to utilise in order to predict earthquakes,” said Dr Dan Faulkner, senior lecturer in rock mechanics at the University of Liverpool.

“Earthquake prediction will only become possible with a detailed knowledge of the earthquake process. Even then, it may still be impossible.”

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Eastern U.S. Quake a wake-up call

Quake a wake-up call for Eastern U.S. – CNN.com.

Volunteers help restock shelves in Mineral, Virginia, just a few miles from the epicenter of Tuesday's earthquake.

Volunteers help restock shelves in Mineral, Virginia, just a few miles from the epicenter of Tuesday’s earthquake.
STORY HIGHLIGHTS
  • Christa von Hillebrandt-Andrade: Easterners don’t expect an earthquake
  • Because quakes are rare in the Eastern U.S., people didn’t know what to do, she says
  • She says they should prepare for quakes just as they do for hurricanes and storms
  • 2004 tsunami an example of a disaster that people didn’t see coming, she says

Editor’s note: Christa von Hillebrandt-Andrade is manager of the Caribbean Tsunami Warning Program of the U.S. National Weather Service and president of the Seismological Society of America.

Mayaguez, Puerto Rico (CNN) — The East Coast of the United States was shaken up by a moderate earthquake on Tuesday that was felt from Maine to Florida, Virginia to Illinois. On TV we saw people run out of buildings, thinking it might be a terrorist attack. Social media was buzzing with comments and testimonies.

Although seismologists, historians and emergency managers have recognized the potential for an earthquake along the East Coast for years, most people were caught by surprise and so responded inappropriately. The ground doesn’t shake as much in the East as it does in California, Alaska, the Pacific Northwest, Puerto Rico or the Virgin Islands. But because of the great concentration of population and infrastructure in the East, it’s an area of immense risk.

Since earthquakes are infrequent in this region, most people don’t know earthquake preparedness measures. Instead of running out of buildings, they should have dropped, covered and held on. Earthquakes are natural phenomena that become disasters when we don’t prepare adequately — or are not educated in proper measures.

The 2004 tsunami is an example of a rare event catching people unprepared, with catastrophic results. In December of that year, more than 230,000 lives were lost in countries around the Indian Ocean. Residents and tourists were taken by surprise — they were not warned, nor did they recognize the natural signs.

Christa von Hillebrandt-Andrade
Christa von Hillebrandt-Andrade

Just this past March, Japan was struck by a tsunami much larger than any in historical memory. Although the country had a state-of-the-art tsunami warning system — which indeed saved tens of thousands of lives — the infrequency of such a mega-tsunami led many to underestimate the threat.

In the Caribbean, we have been working for almost 15 years on our “forgotten danger,” tsunamis, which have claimed over 3,510 people just in the past 160 years, more than in Alaska, Hawaii and the West Coast of the US during the same time period. But we still do not have a tsunami warning center in the region.

In earthquake country, children are taught and practice in schools to “drop, cover and hold.” Radio and TV announcements and newspapers remind people they need to practice sound earthquake design, anchor down furniture, have insurance and be ready to be on their own for many hours, if not days, when a big one strikes. Earthquakes become part of the culture.

Quake caused communications meltdown

Just the way people who live in the Eastern United States prepare for hurricanes, storms and terrorist attacks, the region needs to become earthquake-ready. This could save their lives at home, in another part of the country or the world.

In 2004, Tilly Smith, a 10-year-old girl from England vacationing in Indonesia, saved countless lives because she had learned in school about tsunamis, recognized the natural warning signs and, with her mother, guided people to safety. Earthquake and tsunami education and preparedness is important for all, everywhere.

Just as individuals need to prepare, local, state and federal government officials need to perform earthquake hazard assessments to determine and enforce building codes and take other measures to protect lives and property. As we saw on Tuesday, earthquakes can and will strike at any moment. We can’t afford to let their infrequency lull us into inaction. This earthquake was a wake-up call.

The opinions in this commentary are solely those of Christa von Hillebrandt-Andrade.

Antarctica rising as ice caps melt

Antarctica rising as ice caps melt – environment – 31 July 2011 – New Scientist.

ANTARCTICA is rising like a cheese soufflé: slowly but surely. Lost ice due to climate change and left-over momentum from the end of the last big ice age mean the buoyant continent is heaven-bound.

Donald Argus of NASA’s Jet Propulsion Laboratory in Pasadena, California, and colleagues used 15 years of GPS data to show that parts of the Ellsworth mountains in west Antarctica are rising by around 5 millimetres a year (Geophysical Research Letters, DOI: 10.1029/2011gl048025). Elsewhere on the continent, the rise is slower.

A faster rise has been seen in Greenland, which is thought to be popping up by 4 centimetres a year.

Ongoing climate change could be partly to blame: Antarctica is losing about 200 gigatonnes of ice per year, and for Greenland the figure is 300 gigatonnes. Earth’s continents sit on viscous magma, so the effect of this loss is like taking a load off a dense foam mattress.

But there is another possible contributor. “The Earth has a very long memory,” says Argus. As a result, “there is also a viscous response to ice loss from around 5000 to 10,000 years ago going on”.

Despite this effect, the known ice loss at both poles suggests that embedded in the local rises is a signal of current climate change – researchers just have to tease it out.

climate sceptics take note: raw data you wanted now available

OK, climate sceptics: here’s the raw data you wanted – environment – 28 July 2011 – New Scientist.

Anyone can now view for themselves the raw data that was at the centre of last year’s “climategate” scandal.

Temperature records going back 150 years from 5113 weather stations around the world were yesterday released to the public by the Climatic Research Unit (CRU) at the University of East Anglia in Norwich, UK. The only records missing are from 19 stations in Poland, which refused to allow them to be made public.

“We released [the dataset] to dispel the myths that the data have been inappropriately manipulated, and that we are being secretive,” says Trevor Davies, the university’s pro-vice-chancellor for research. “Some sceptics argue we must have something to hide, and we’ve released the data to pull the rug out from those who say there isn’t evidence that the global temperature is increasing.”

Hand it over

The university were ordered to release data by the UK Information Commissioner’s Office, following a freedom-of-information request for the raw data from researchers Jonathan Jones of the University of Oxford and Don Keiller of Anglia Ruskin University in Cambridge, UK.

Davies says that the university initially refused on the grounds that the data is not owned by the CRU but by the national meteorological organisations that collect the data and share it with the CRU.

When the CRU’s refusal was overruled by the information commissioner, the UK Met Office was recruited to act as a go-between and obtain permission to release all the data.

Poland refused, and the information commissioner overruled Trinidad and Tobago’s wish for the data it supplied on latitudes between 30 degrees north and 40 degrees south to be withheld, as it had been specifically requested by Jones and Keiller in their FOI request and previously shared with other academics.

The price

The end result is that all the records are there, except for Poland’s. Davies’s only worry is that the decision to release the Trinidad and Tobago data against its wishes may discourage the open sharing of data in the future. Other research organisations may from now on be reluctant to pool data they wish to be kept private.

Thomas Peterson, chief scientist at the National Climatic Data Center of the US National Oceanographic and Atmospheric Administration (NOAA) and president of the Commission for Climatology at the World Meteorological Organization, agrees there might be a cost to releasing the data.

“I have historic temperature data from automatic weather stations on the Greenland ice sheet that I was able to obtain from Denmark only because I agreed not to release them,” he says. “If countries come to expect that sharing of any data with anyone will eventually lead to strong pressure for them to fully release those data, will they be less willing to collaborate in the future?”

Davies is confident that genuine and proper analysis of the raw data will reproduce the same incontrovertible conclusion – that global temperatures are rising. “The conclusion is very robust,” he says, explaining that the CRU’s dataset of land temperatures tally with those from other independent research groups around the world, including those generated by the NOAA and NASA.

“Should people undertake analyses and come up with different conclusions, the way to present them is through publication in peer-reviewed journals, so we know it’s been through scientific quality control,” says Davies.

No convincing some people

Other mainstream researchers and defenders of the consensus are not so confident that the release will silence the sceptics. “One can hope this might put an end to the interminable discussion of the CRU temperatures, but the experience of GISTEMP – another database that’s been available for years – is that the criticisms will continue because there are some people who are never going to be satisfied,” says Gavin Schmidt of Columbia University in New York.

“Sadly, I think this will just lead to a new round of attacks on CRU and the Met Office,” says Bob Ward, communications director of the Grantham Research Institute on Climate Change and the Environment at the London School of Economics. “Sceptics will pore through the data looking for ways to criticise the processing methodology in an attempt to persuade the public that there’s doubt the world has warmed significantly.”

The CRU and its leading scientist, Phil Jones, were at the centre of the so-called “climategate” storm in 2009 when the unit was accused of withholding and manipulating data. It was later cleared of the charge.

Climate change disasters can be predicted, study suggests

Climate change disasters can be predicted, study suggests.

ScienceDaily (June 19, 2011) — Climate change disasters, such as the melting of the Greenland ice sheet, dieback of the Amazon rainforest or collapse of the Atlantic overturning circulation, can be predicted according to University of Exeter research.

Writing in the journal Nature Climate Change, Professor Tim Lenton of the University of Exeter shows that the ‘tipping points’ that trigger these disasters could be anticipated by looking for changes in climate behaviour.

Climate ‘tipping points’ are small changes that trigger a massive shift in climate systems, with potentially devastating consequences. It is already known that climate change caused by human activity could push several potential hazards past their ‘tipping point’. However, it is often assumed that these ‘tipping points’ are entirely unpredictable.

Professor Lenton argues that a system of forecasting could be developed to enable some forewarning of high-risk tipping points. The approach he outlines involves analysing observational data to look for signs that a climate system is slowing down in its response to short-term natural variability (which we experience as the weather). This characteristic behaviour indicates the climate is becoming unstable, and is a common feature of systems approaching critical thresholds known as ‘bifurcation points’.

Professor Tim Lenton of the University of Exeter said: “Many people assume that tipping points which could be passed as a result of human-induced climate change are essentially unpredictable. Recent research shows that the situation is not as hopeless as it may seem: we have the tools to anticipate thresholds, which means we could give societies valuable time to adapt.

“Although these findings give us hope, we are still a long way from developing rigorous early warning systems for these climate hazards.”

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Exeter.


Journal Reference:

  1. Timothy M. Lenton. Early warning of climate tipping points. Nature Climate Change, 2011; DOI: 10.1038/nclimate1143

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Are we entering an age of major earthquakes?

Are we entering an age of major earthquakes? – CSMonitor.com.

A study of more than a century of global seismic records has prompted some scientists to say that major earthquakes have tended to occur in clusters. Others disagree.

Japan Ground Self-Defense Force members search in the rain for victims’ belongings in a devastated area in Minami Soma, northeastern Japan, Tuesday.

Hiro Komae/AP

Enlarge

By Charles Q. Choi, OurAmazingPlanet Contributor / April 20, 2011

A number of devastating quakes have struck across the globe in recent years — from Japan to Chile to Haiti — sparking fears that our planet is due to experience even more catastrophic temblors in the near future.

Skip to next paragraph

Three research teams have now combed through 110 years’ worth of global seismic records to see if we might be caught in a global trend of giant earthquakes.

Some say we are; others disagree.

Megaquake clusters

One pair of researchers found clusters of what they called “megaquakes,” earthquakes of magnitude 9.0 or greater.

One cluster involved three such quakes between 1952 and 1964, including the magnitude 9.5 Chile quake of 1960, the largest earthquake ever recorded on Earth. Another, larger, cluster of magnitude 8.6 and higher temblors happened between 1950 to 1965, said Charles Bufe and David Perkins, seismologists with the U.S. Geological Survey in Golden, Colo. They speculate that the magnitude 8.4 Peru quake in 2001 could mark the beginning of a new global sequence of major quakes that we are currently experiencing.

“This isn’t doomsday — I don’t think large earthquakes will occur over a long period of time — but we’re saying there seems to be a cluster right now with a higher than normal probability for large quakes,” Bufe told OurAmazingPlanet. “I don’t know how long this cluster might last — if we don’t get another large earthquake in maybe the next 10 or 12 years, I would say we’re probably out of the cluster.”

Bufe suggested that by sending seismic waves traveling around and around the planet’s surface, very large earthquakes might weaken fault zones that are already very close to failure. “I think there’s a more than 50 percent chance we’ll see another magnitude 9 quake sometime in the next decade or so,” he said.

Just chance?

On the other hand, this apparent recent spike in large quakes could just reflect random fluctuations in global patterns of seismic activity. A statistical study from U.S. Geological Survey researcher Andrew Michael at Menlo Park, Calif., suggests this seeming cluster pattern disappeared once local aftershocks of the large earthquakes are taken into account.

“The most important lesson is that random doesn’t mean uniformly distributed in time — instead, random processes create apparent clustering and it is important to carefully consider whether apparent clusters, or times of less activity, go beyond what is expected from a simple random process,” Michael told OurAmazingPlanet. “So far, my results show that the apparent clustering is consistent with a random process.”

If the apparent clustering of these quakes is a matter of chance, then seismologists can’t say whether or not another huge temblor is likely to erupt anytime soon.

“The recent spate of great earthquakes can be explained as a random fluctuation without predictive power for the future,” Michael said. He added that global predictions of earthquakes and the damage they inflict should use the longest possible historical record for an area “rather than focusing on the recent past.”

Long-term record

Seismologist Richard Aster at the New Mexico Institute of Mining and Technology and his colleagues looked at historical catalogs of earthquakes along with more recent findings to create a long-term record of the cumulative size of earthquakes around the world.

They suggest there were relatively low rates of big earthquakes during the periods 1907 to 1950 and 1967 to 2004. However, they found the rate of large earthquakes increased substantially during the period 1950 to 1967 and appears to be on the rise again since 2004, since the devastating magnitude 9.1 to 9.3 earthquake that struck Indonesia and generated a massive tsunami late that year.

Still, this finding “is not statistically differentiable from randomness,” Aster told OurAmazingPlanet.

Progress into understanding whether there are ages of major quakes or not may be slow “because we just don’t get that many great earthquakes to produce a better sampling of this natural process,” Aster said.

“We only get a few magnitude 9-plus earthquakes per century, for example — fortunately for earthquake risks around the world, these events are rare,” Aster said. “There are only 14 earthquakes in the past 111 years greater than magnitude 8.5.”

Michael agreed. “The main limitation is that we don’t have enough data,” he said. “We can’t say that clustering doesn’t exist. We can only say that the data doesn’t let us reject the hypothesis that the data is random. If there was more data, then the results could change — but that will take decades to occur.”

The scientists detailed their findings on April 14 at the Seismological Society of America meeting in Memphis, Tenn.

Are we entering an age of major earthquakes?

Are we entering an age of major earthquakes? – CSMonitor.com.

A study of more than a century of global seismic records has prompted some scientists to say that major earthquakes have tended to occur in clusters. Others disagree.

Japan Ground Self-Defense Force members search in the rain for victims’ belongings in a devastated area in Minami Soma, northeastern Japan, Tuesday.

Hiro Komae/AP

By Charles Q. Choi, OurAmazingPlanet Contributor / April 20, 2011

A number of devastating quakes have struck across the globe in recent years — from Japan to Chile to Haiti — sparking fears that our planet is due to experience even more catastrophic temblors in the near future.

Skip to next paragraph

Three research teams have now combed through 110 years’ worth of global seismic records to see if we might be caught in a global trend of giant earthquakes.

Some say we are; others disagree.

Megaquake clusters

One pair of researchers found clusters of what they called “megaquakes,” earthquakes of magnitude 9.0 or greater.

One cluster involved three such quakes between 1952 and 1964, including the magnitude 9.5 Chile quake of 1960, the largest earthquake ever recorded on Earth. Another, larger, cluster of magnitude 8.6 and higher temblors happened between 1950 to 1965, said Charles Bufe and David Perkins, seismologists with the U.S. Geological Survey in Golden, Colo. They speculate that the magnitude 8.4 Peru quake in 2001 could mark the beginning of a new global sequence of major quakes that we are currently experiencing.

“This isn’t doomsday — I don’t think large earthquakes will occur over a long period of time — but we’re saying there seems to be a cluster right now with a higher than normal probability for large quakes,” Bufe told OurAmazingPlanet. “I don’t know how long this cluster might last — if we don’t get another large earthquake in maybe the next 10 or 12 years, I would say we’re probably out of the cluster.”

Bufe suggested that by sending seismic waves traveling around and around the planet’s surface, very large earthquakes might weaken fault zones that are already very close to failure. “I think there’s a more than 50 percent chance we’ll see another magnitude 9 quake sometime in the next decade or so,” he said.

Just chance?

On the other hand, this apparent recent spike in large quakes could just reflect random fluctuations in global patterns of seismic activity. A statistical study from U.S. Geological Survey researcher Andrew Michael at Menlo Park, Calif., suggests this seeming cluster pattern disappeared once local aftershocks of the large earthquakes are taken into account.

“The most important lesson is that random doesn’t mean uniformly distributed in time — instead, random processes create apparent clustering and it is important to carefully consider whether apparent clusters, or times of less activity, go beyond what is expected from a simple random process,” Michael told OurAmazingPlanet. “So far, my results show that the apparent clustering is consistent with a random process.”

If the apparent clustering of these quakes is a matter of chance, then seismologists can’t say whether or not another huge temblor is likely to erupt anytime soon.

“The recent spate of great earthquakes can be explained as a random fluctuation without predictive power for the future,” Michael said. He added that global predictions of earthquakes and the damage they inflict should use the longest possible historical record for an area “rather than focusing on the recent past.”

Long-term record

Seismologist Richard Aster at the New Mexico Institute of Mining and Technology and his colleagues looked at historical catalogs of earthquakes along with more recent findings to create a long-term record of the cumulative size of earthquakes around the world.

They suggest there were relatively low rates of big earthquakes during the periods 1907 to 1950 and 1967 to 2004. However, they found the rate of large earthquakes increased substantially during the period 1950 to 1967 and appears to be on the rise again since 2004, since the devastating magnitude 9.1 to 9.3 earthquake that struck Indonesia and generated a massive tsunami late that year.

Still, this finding “is not statistically differentiable from randomness,” Aster told OurAmazingPlanet.

Progress into understanding whether there are ages of major quakes or not may be slow “because we just don’t get that many great earthquakes to produce a better sampling of this natural process,” Aster said.

“We only get a few magnitude 9-plus earthquakes per century, for example — fortunately for earthquake risks around the world, these events are rare,” Aster said. “There are only 14 earthquakes in the past 111 years greater than magnitude 8.5.”

Michael agreed. “The main limitation is that we don’t have enough data,” he said. “We can’t say that clustering doesn’t exist. We can only say that the data doesn’t let us reject the hypothesis that the data is random. If there was more data, then the results could change — but that will take decades to occur.”

The scientists detailed their findings on April 14 at the Seismological Society of America meeting in Memphis, Tenn.

California big one expected to pale next to Japan quake

California big one expected to pale next to Japan quake | Reuters.

 

The skyline of San Francisco and the Golden Gate Bridge appear above the evening fog as the suns sets on the Marin Headlands in Sausalito, California April 18, 2009.

Credit: Reuters/Robert Galbraith

LOS ANGELES | Wed Mar 16, 2011 4:20pm EDT

LOS ANGELES (Reuters) – When the seismic “big one” hits California, scientists doubt it will be quite as powerful as the earthquake that struck Japan last week although it could do plenty of damage.

The colossal California quake considered inevitable and long overdue is most likely to strike along the southern end of the famed San Andreas Fault and register a magnitude of 7.5 or greater, many times less powerful than the 9.0 temblor that rocked Japan on Friday, geologists say.

Still, an earthquake damage forecast prepared in 2008 for the U.S. Geological Survey by geophysicists and engineers envisions a calamity that would leave 2,000 people dead, 50,000 injured and 250,000 homeless.

That scenario is based on the premise of a magnitude 7.8 quake rupturing the San Andreas in the desert east of Los Angeles and radiating with catastrophic fury into the nation’s second-largest metropolitan area.

Such a quake could be expected to topple 1,500 buildings, badly damage another 300,000 and sever highways, power lines, pipelines, railroads, communications networks and aqueducts. Property losses of more than $200 billion are projected.

The hypothetical quake also would ignite about 1,600 fires, some growing into conflagrations that would engulf hundreds of city blocks.

Experts predict the biggest long-term economic disruption would come from damage to water-distribution systems that would leave some homes and businesses without running water for months.

“The lesson is you don’t need a magnitude 9 to cause extensive damage,” said USGS spokeswoman Leslie Gordon.

The quake scenario for the southern San Andreas does not foresee damage to the nearest of the state’s two nuclear power plants, the Southern California Edison-owned San Onofre station between Los Angeles and San Diego.

Both Edison and Pacific Gas & Electric, owner of the Diablo Canyon plant to the north at San Luis Obispo, say their facilities are built to withstand quakes far greater than nearby faults are capable of producing.

And unlike Japan, California faces little if any risk of tsunamis from its own quakes.

But substandard construction poses a bigger problem in California, said Lucy Jones, a USGS geologist who co-authored the agency’s quake scenario.

“The Japanese have done a better job than we have done of retrofitting older buildings,” she said on Tuesday.

SEISMIC ODDS

USGS studies put the probability of California being hit by a quake measuring 7.5 or more in the next 30 years at 46 percent, though the extent of damage will depend on where in the state it occurs. The likelihood of a 6.7 quake, comparable in size to the temblors that rocked San Francisco in 1989 and Los Angeles in 1994, is 99 percent statewide.

The Los Angeles basin is especially vulnerable to violent shaking from earthquakes because the area is heavily populated and built on motion-sensitive sediment that runs four miles deep before hitting bedrock, USGS geologist Erik Pounders said.

The 9.0 quake that struck Friday off Japan‘s northeast coast, unleashing a deadly tsunami and a nuclear power crisis, was the biggest in that island nation’s modern history. The death toll is expected to surpass 10,000, and the quake ranks as the fifth most powerful in the world for the past century.

Its force was roughly equivalent to the power of 30 quakes like the one imagined in the 2008 USGS scenario.

Geologists believe a 9.0 quake is virtually impossible along the San Andreas, a network of “strike-slip” faults smaller and more fragmented than the great chasm that exists where two continent-sized plates of the Earth’s crust meet along the Japanese islands.

This subduction zone beneath the Pacific, where one tectonic plate is thrust up over another, is capable of producing the biggest quakes on Earth, on an order of magnitude higher than any recorded in California.

Offshore quakes generated from subduction zones, also found along Alaska’s Aleutian Islands chain, can produce tsunamis because of the tremendous volume of water they suddenly displace on the sea floor.

The horizontal ruptures of California’s seismic faults, even those offshore, displace little or no water, and thus pose no tsunami threat, except in cases when they trigger underwater landslides. Even those tsunamis, however, are small compared with the ones caused by subduction quakes at sea.

At the high end of quake magnitudes considered possible in California was the massive rupture of the San Andreas Fault in northern California which caused the devastating 8.3 quake that laid waste to San Francisco in 1906.

The last “big one” of equivalent size to strike south of the San Gabriel Mountains, near Los Angeles, was some 300 years ago, and the average interval between such quakes in that region is 150 years.

(Editing by Dan Whitcomb and Jerry Norton)

Japan tsunami and earthquake

Japan tsunami and earthquake – live coverage | World news | guardian.co.uk.

VIDEO: Narrow escape for Japan office workers

Office workers have narrowly escaped harm by falling debris after a massive earthquake rocked Japan.

 

VIDEO: Eyewitness video of Japan quake

Flames rise from houses and debris from the tsunami in Sendai, Miyagi Prefecture Burning houses and debris after the tsunami in Sendai, Miyagi prefecture, Japan. Photograph: AP

Guardian environment team : Felicity Carus

7.47pm GMT: Felicity Carus is on the west coast of the US, watching the reaction to the huge waves generated by the tsunami arriving there:

Tens of thousands of people were evacuated from coastal and low lying areas along the west coast of the US this morning as seven-foot waves generated by the 8.9 earthquake near Japan first struck the US mainland coast at Crescent City, 20 miles south of the Oregon border.

The West Coast and Alaska Tsunami Warning Centre issued a warning for the California coast after waves travelled at 500 miles an hour across the Pacific, hitting Hawaii with waves up to 11ft high.

The first surges hit the US mainland at around 7.30am local time. Schools, highways and national parks were closed as authorities urged people to stay away from beaches, jetties and harbours.

Sirens sounded across Crescent City in far northern California in the early morning and police went door to door evacuating homes in the tsunami impact zone along the coast as fishermen left the busy harbour. A tsunami in 1964 devastated Crescent City and killed 11 people. Surges were expected continue to hit the California coast for up to 12 hours.

In the event, Crescent City experienced increasingly large waves from 3ft at 8.15am rising to 8.1ft at 10.15am. Some 6,000 people were evacuated from Crescent City town and police have sealed off the harbour.

In San Francisco police closed the city’s Great Highway and the National Park Service closed Ocean Beach, Baker Beach, China Beach, Fort Funston and Aquatic Park tucked inside the bay. Transport services to these areas were stopped and boats took shelter within the bay. There were also concerns that surging waves would pass under the Golden Gate Bridge and flood low-lying areas within the Bay Area, but low tide was expected to reduce their full force.

7.41pm GMT: A Japanese minister says a radioactive leak likely to come from the damaged nuclear plant in Fukushima – 240km (150 miles) north of Tokyo – is expected to be small. Reuters reports:

“It’s possible that radioactive material in the reactor vessel could leak outside but the amount is expected to be small and the wind blowing towards the sea will be considered,” Chief Cabinet Yukio Edano told a news conference.

“Residents are safe after those within a 3km radius were evacuated and those within a 10km radius are staying indoors, so we want people to be calm,” he added.

The plant’s operator, Tokyo Electric Power Co, said pressure had built up inside a reactor at the plant after the cooling system was knocked out by the earthquake, the largest on record in Japan. The company had been operating three out of the six reactors at the Fukushima Daiichi plant at the time of the quake, all of which shut down. The remaining three had already been shut down for planned maintenance.

7.35pm GMT: Police in Miyagi prefecture say 200-300 bodies have been found in the northeastern coastal city of Sendai, the city closest to the epicenter of today’s first earthquake. Another 151 were confirmed killed, with 547 missing. Police also said around 800 people were injured.

7.28pm GMT: Ecuador’s president Rafael Correa has declared a national state of emergency and urged coastal and island residents to evacuate fast to higher areas, as the tsunami approaches.

7.23pm GMT: The US Geological Survey has said the new quake around Nagano a few minutes ago was measured at 6.2 magnitude – a big quake in most places. It’s 4.23am in Japan and I suspect quite a few people have had an early wake-up jolt.

7.16pm GMT: A 6.6 magnitude shock has just been reported in the Nagano Niigata area of Japan, apparently on a different faultline from the 8.9 magnitude quake earlier.

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TOKYO | Fri Mar 11, 2011 6:01pm EST

TOKYO (Reuters) – Japan confronted devastation along its northeastern coast on Saturday, with fires raging and parts of some cities under water after a massive earthquake and tsunami that likely killed at least 1,000 people.

Daybreak was expected to reveal the full extent of the death and damage from Friday’s 8.9 magnitude earthquake and the 10-meter high tsunami it sent surging into cities and villages, sweeping away everything in its path.

In one of the worst-hit residential areas, people buried under rubble could be heard calling out “help” and “when are we going to be rescued,” Kyodo news agency reported.

The government warned there could be a small radiation leak from a nuclear reactor whose cooling system was knocked out by the quake. Prime Minister Naoto Kan ordered an evacuation zone around the plant be expanded to 10 km (6 miles) from 3 km. Some 3,000 people had earlier been moved out of harm’s way.

Underscoring concerns about the Fukushima plant, 240 km (150 miles) north of Tokyo, U.S. officials said Japan had asked for coolant to avert a rise in the temperature of its nuclear rods, but ultimately handled the matter on its own. Officials said a leak was still possible because pressure would have to be released.

The unfolding natural disaster prompted offers of search and rescue help from 45 countries.

China said rescuers were ready to help with quake relief while President Barack Obama told Japanese Prime Minister Naoto Kan the United States would assist in any way.

“This is likely to be a humanitarian relief operation of epic proportions,” Japan expert Sheila Smith of the U.S.-based Council on Foreign Relations wrote in a commentary.

The northeastern Japanese city of Kesennuma, with a population of 74,000, was hit by widespread fires and one-third of the city was under water, Jiji news agency said on Saturday.

The airport in the city of Sendai, home to one million people, was on fire, it added.

TV footage from Friday showed a muddy torrent of water carrying cars and wrecked homes at high speed across farmland near Sendai, 300 km (180 miles) northeast of Tokyo. Ships had been flung onto a harbor wharf, where they lay helplessly on their side.

Boats, cars and trucks were tossed around like toys in the water after a small tsunami hit the town of Kamaichi in northern Japan. Kyodo news agency reported that contact had been lost with four trains in the coastal area.

Japanese politicians pushed for an emergency budget to fund relief efforts after Kan asked them to “save the country,” Kyodo news agency reported. Japan is already the most heavily indebted major economy in the world, meaning any funding efforts would be closely scrutinized by financial markets.

Domestic media said the death toll was expected to exceed 1,000, most of whom appeared to have drowned by churning waters.

The extent of the destruction along a lengthy stretch of coastline suggested the death toll could rise significantly.

Even in a nation accustomed to earthquakes, the devastation was shocking.

“A big area of Sendai city near the coast, is flooded. We are hearing that people who were evacuated are stranded,” said Rie Sugimoto, a reporter for NHK television in Sendai.

“About 140 people, including children, were rushed to an elementary school and are on the rooftop but they are surrounded by water and have nowhere else to go.”

Japan has prided itself on its speedy tsunami warning system, which has been upgraded several times since its inception in 1952, including after a 7.8 magnitude quake triggered a 30-meter high wave before a warning was given.

The country has also built countless breakwaters and floodgates to protect ports and coastal areas, although experts said they might not have been enough to prevent disasters such as the one that struck on Friday.

In Tokyo, many residents who had earlier fled swaying buildings slept in their offices after public transport was shut down. Many subways in Tokyo later resumed operation but trains did not run.

“I was unable stay on my feet because of the violent shaking. The aftershocks gave us no reprieve. Then the tsunamis came when we tried to run for cover. It was the strongest quake I experienced,” a woman with a baby on her back told television in northern Japan.

FIRES ACROSS THE COAST

The quake, the most powerful since Japan started keeping records 140 years ago, sparked at least 80 fires in cities and towns along the coast, Kyodo said.

Other Japanese nuclear power plants and oil refineries were shut down and one refinery was ablaze.

Auto plants, electronics factories and refineries shut, roads buckled and power to millions of homes and businesses was knocked out. Several airports, including Tokyo’s Narita, were closed and rail services halted. All ports were shut.

The central bank said it would cut short a two-day policy review scheduled for next week to one day on Monday and promised to do its utmost to ensure financial market stability.

The disaster occurred as the world’s third-largest economy had been showing signs of reviving from an economic contraction in the final quarter of last year. It raised the prospect of major disruptions for many key businesses and a massive repair bill running into tens of billions of dollars.

The tsunami alerts revived memories of the giant waves that struck Asia in 2004.

Warnings were issued for countries to the west of Japan and across the Pacific as far away as Colombia and Peru, but the tsunami dissipated as it sped across the ocean and worst fears in the Americas were not realised.

The earthquake was the fifth most powerful to hit the world in the past century.

“The building shook for what seemed a long time and many people in the newsroom grabbed their helmets and some got under their desks,” Reuters correspondent Linda Sieg said in Tokyo. “It was probably the worst I have felt since I came to Japan more than 20 years ago.”

The quake surpasses the Great Kanto quake of September 1, 1923, which had a magnitude of 7.9 and killed more than 140,000 people in the Tokyo area.

The 1995 Kobe quake caused $100 billion in damage and was the most expensive natural disaster in history. Economic damage from the 2004 Indian Ocean tsunami was estimated at about $10 billion.

Earthquakes are common in Japan, one of the world’s most seismically active areas. (Writing by John Chalmers; Editing by Dean Yates)

Yellowstone Has Bulged as Magma Pocket Swells

Yellowstone Has Bulged as Magma Pocket Swells.

Steam rising from Castle Geyser in Yellowstone National Park.

Steam rises from Castle Geyser in Yellowstone National Park (file photo).

Photograph by Mark Thiessen, National Geographic

Brian Handwerk

for National Geographic News

Published January 19, 2011

Yellowstone National Park‘s supervolcano just took a deep “breath,” causing miles of ground to rise dramatically, scientists report.

The simmering volcano has produced major eruptions—each a thousand times more powerful than Mount St. Helens’s 1980 eruption—three times in the past 2.1 million years. Yellowstone’s caldera, which covers a 25- by 37-mile (40- by 60-kilometer) swath of Wyoming, is an ancient crater formed after the last big blast, some 640,000 years ago.

(See “When Yellowstone Explodes” in National Geographic magazine.)

Since then, about 30 smaller eruptions—including one as recent as 70,000 years ago—have filled the caldera with lava and ash, producing the relatively flat landscape we see today.

But beginning in 2004, scientists saw the ground above the caldera rise upward at rates as high as 2.8 inches (7 centimeters) a year. (Related: “Yellowstone Is Rising on Swollen ‘Supervolcano.'”)

The rate slowed between 2007 and 2010 to a centimeter a year or less. Still, since the start of the swelling, ground levels over the volcano have been raised by as much as 10 inches (25 centimeters) in places.

“It’s an extraordinary uplift, because it covers such a large area and the rates are so high,” said the University of Utah’s Bob Smith, a longtime expert in Yellowstone’s volcanism.

Video: Yellowstone—World’s First National Park.

Scientists think a swelling magma reservoir four to six miles (seven to ten kilometers) below the surface is driving the uplift. Fortunately, the surge doesn’t seem to herald an imminent catastrophe, Smith said. (Related: “Under Yellowstone, Magma Pocket 20 Percent Larger Than Thought.”)

“At the beginning we were concerned it could be leading up to an eruption,” said Smith, who co-authored a paper on the surge published in the December 3, 2010, edition of Geophysical Research Letters.

“But once we saw [the magma] was at a depth of ten kilometers, we weren’t so concerned. If it had been at depths of two or three kilometers [one or two miles], we’d have been a lot more concerned.”

Studies of the surge, he added, may offer valuable clues about what’s going on in the volcano’s subterranean plumbing, which may eventually help scientists predict when Yellowstone’s next volcanic “burp” will break out.

Yellowstone Takes Regular Breaths

Smith and colleagues at the U.S. Geological Survey (USGS) Yellowstone Volcano Observatory have been mapping the caldera’s rise and fall using tools such as global positioning systems (GPS) and interferometric synthetic aperture radar (InSAR), which gives ground-deformation measurements.

Ground deformation can suggest that magma is moving toward the surface before an eruption: The flanks of Mount St. Helens, for example, swelled dramatically in the months before its 1980 explosion. (See pictures of Mount St. Helens before and after the blast.)

But there are also many examples, including the Yellowstone supervolcano, where it appears the ground has risen and fallen for thousands of years without an eruption.

According to current theory, Yellowstone’s magma reservoir is fed by a plume of hot rock surging upward from Earth’s mantle. (Related: “New Magma Layer Found Deep in Earth’s Mantle?”)

When the amount of magma flowing into the chamber increases, the reservoir swells like a lung and the surface above expands upward. Models suggest that during the recent uplift, the reservoir was filling with 0.02 cubic miles (0.1 cubic kilometer) of magma a year.

When the rate of increase slows, the theory goes, the magma likely moves off horizontally to solidify and cool, allowing the surface to settle back down.

Based on geologic evidence, Yellowstone has probably seen a continuous cycle of inflation and deflation over the past 15,000 years, and the cycle will likely continue, Smith said.

Surveys show, for example, that the caldera rose some 7 inches (18 centimeters) between 1976 and 1984 before dropping back about 5.5 inches (14 centimeters) over the next decade.

“These calderas tend to go up and down, up and down,” he said. “But every once in a while they burp, creating hydrothermal explosions, earthquakes, or—ultimately—they can produce volcanic eruptions.”

Yellowstone Surge Also Linked to Geysers, Quakes?

Predicting when an eruption might occur is extremely difficult, in part because the fine details of what’s going on under Yellowstone are still undetermined. What’s more, continuous records of Yellowstone’s activity have been made only since the 1970s—a tiny slice of geologic time—making it hard to draw conclusions.

“Clearly some deep source of magma feeds Yellowstone, and since Yellowstone has erupted in the recent geological past, we know that there is magma at shallower depths too,” said Dan Dzurisin, a Yellowstone expert with the USGS Cascades Volcano Observatory in Washington State.

“There has to be magma in the crust, or we wouldn’t have all the hydrothermal activity that we have,” Dzurisin added. “There is so much heat coming out of Yellowstone right now that if it wasn’t being reheated by magma, the whole system would have gone stone cold since the time of the last eruption 70,000 years ago.”

The large hydrothermal system just below Yellowstone’s surface, which produces many of the park’s top tourist attractions, may also play a role in ground swelling, Dzurisin said, though no one is sure to what extent.

“Could it be that some uplift is caused not by new magma coming in but by the hydrothermal system sealing itself up and pressurizing?” he asked. “And then it subsides when it springs a leak and depressurizes? These details are difficult.”

And it’s not a matter of simply watching the ground rise and fall. Different areas may move in different directions and be interconnected in unknown ways, reflecting the as yet unmapped network of volcanic and hydrothermal plumbing.

The roughly 3,000 earthquakes in Yellowstone each year may offer even more clues about the relationship between ground uplift and the magma chamber.

For example, between December 26, 2008, and January 8, 2009, some 900 earthquakes occurred in the area around Yellowstone Lake.

This earthquake “swarm” may have helped to release pressure on the magma reservoir by allowing fluids to escape, and this may have slowed the rate of uplift, the University of Utah’s Smith said. (Related: “Mysterious ‘Swarm’ of Quakes Strikes Oregon Waters.”)

“Big quakes [can have] a relationship to uplift and deformations caused by the intrusion of magma,” he said. “How those intrusions stress the adjacent faults, or how the faults might transmit stress to the magma system, is a really important new area of study.”

Overall, USGS’s Dzurisin added, “the story of Yellowstone deformation has gotten more complex as we’ve had better and better technologies to study it.”