Another Large Earthquake Off Coast Of Sumatra Likely

ScienceDaily (Dec. 4, 2008) — The subduction zone that brought us the 2004 Sumatra-Andaman earthquake and tsunami is ripe for yet another large event, despite a sequence of quakes that occurred in the Mentawai Islands area in 2007, according to a group of earthquake researchers led by scientists from the Tectonics Observatory at the California Institute of Technology (Caltech).

"From what we saw," says geologist Jean-Philippe Avouac, director of the Tectonics Observatory and one of the paper's lead authors, "we can say with some confidence that we're probably not done with large earthquakes in Sumatra."

The devastating magnitude 9.2 earthquake that occurred off the western coast of Sumatra on December 26, 2004—the earthquake that spawned a lethal tsunami throughout the Indian Ocean—took place in a subduction zone, an area where one tectonic plate dips under another, forming a quake-prone region.

It is that subduction zone that drew the interest of the Caltech-led team. Seismic activity has continued in the region since the 2004 event, they knew. But have the most recent earthquakes been able to relieve the previous centuries of built-up seismic stress?

Yes . . . and no. Take, for instance, an area just south of the 2004 quake, where a magnitude 8.6 earthquake hit in 2005. (That same area had also been the site of a major earthquake in 1861.) The 2005 quake, says Avouac, did a good job of "unzipping" the stuck area in that patch of the zone, effectively relieving the stresses that had built up since 1861. This means that it should be a few centuries before another large quake in that area would be likely.

The same cannot be said, however, of the area even further south along that same subduction zone, near the Mentawai Islands, a chain of about 70 islands off the western coasts of Sumatra and Indonesia. This area, too, has been hit by giant earthquakes in the past (an 8.8 in 1797 and a 9.0 in 1833). More recently, on September 12, 2007, it experienced two earthquakes just 12 hours apart: first a magnitude 8.4 quake and then a magnitude 7.9.

These earthquakes did not come as a surprise to the Caltech researchers. Caltech geologist and paper coauthor Kerry Sieh, who is now at the Nanyang Technological University in Singapore, had long been using coral growth rings to quantify the pattern of slow uplift and subsidence in the Mentawai Islands area; that pattern, he and his colleagues knew, is the result of stress build-up on the plate interface, which should eventually be released by future large earthquakes.

But was all that accumulated stress released in 2007? In the work described in the Nature letter, the researchers analyzed seismological records, remote sensing (inSAR) data, field measurements, and, most importantly, data gathered by an array of continuously recording GPS stations called SuGAr (for Sumatra Geodetic Array) to find out.

Their answer? The quakes hadn't even come close to doing their stress-reduction job. "In fact," says Ali Ozgun Konca, a Caltech scientist and the paper's first author, who did this work as a graduate student, "we saw release of only a quarter of the moment needed to make up for the accumulated deficit over the past two centuries." (Moment is a measure of earthquake size that takes into account how much the fault slips and over how much area.)

"The 2007 quakes occurred in the right place at the right time," adds Avouac. "They were not a surprise. What was a surprise was that those earthquakes were way smaller than we expected."

"The quake north of this region, in 2005, ruptured completely," says Konca. "But the 2007 sequence of quakes was more complicated. The slippage of the plates was patchy, and it didn't release all the strain that had accumulated."

"It was what we call a partial rupture," adds Avouac. "There's still enough strain to create another major earthquake in that region. We may have to wait a long time, but there's no reason to think it's over."

Their findings were published in a letter in the December 4 issue of the journal Nature.

Other authors on the paper include Anthony Sladen, Aron J. Meltzner, John Galetzka, Jeff Genrich, and Don V. Helmberger from Caltech; Danny H. Natawidjaja from the Indonesian Institute of Science (LIPI); Peng Fang and Yehuda Bock from the Scripps Institution of Oceanography in La Jolla; Zhenhong Li from the University of Glasgow in Scotland; Mohamed Chlieh from the Université de Nice Sophia-Antipolis in France; Eric J. Fielding from the Jet Propulsion Laboratory; and Chen Ji from the University of California, Santa Barbara.

The work was supported by funding from the National Science Foundation and the Gordon and Betty Moore Foundation.

Journal reference:

1. . Partial rupture of a locked patch of the Sumatra megathrust during the 2007 earthquake sequence.Nature, December 4, 2008

Adapted from materials provided by California Institute of Technology, via EurekAlert!, a service of AAAS.

Source :http://www.sciencedaily.com/releases/2008/12/081203131042.htm

Rigorous Earthquake Simulations Aim To Make Buildings Safer

ScienceDaily (Aug. 24, 2008) — Engineering researchers from UC San Diego and the University of Arizona have concluded three months of rigorous earthquake simulation tests on a half-scale three-story structure, and will now begin sifting through their results so they can be used in the future designs of buildings across the nation. The engineers produced a series of earthquake jolts as powerful as magnitude 8.0 on a structure resembling a parking garage.

The one-million pound precast concrete structure is the largest footprint of any structure ever tested on a shake table in the United States. The earthquake tests were conducted at the UC San Diego Jacobs School of Engineering’s Englekirk Structural Engineering Center, which is about eight miles east of the university’s main campus. As part of the project, the researchers are testing the seismic response of precast concrete floor systems used in structures such as parking garages, college dormitories, hotels, stadiums, prisons and office buildings. They are also trying to figure out ways to improve the connections in precast concrete buildings.
“One of the purposes of our research is to develop better designs for precast concrete buildings,” said Jose Restrepo, co-principal investigator of the project and a structural engineering professor at UC San Diego’s Jacobs School of Engineering. “The results of our research have been tremendous.”
Precast concrete, which is built in pieces and then put together to construct buildings, has been a breakthrough in the industry in terms of saving time and money, and increasing durability. While precast concrete has proven to be a robust design material for structures, researchers are working to provide the industry with new methods of connecting these pieces more efficiently.
“This is really important to our industry because we’ll be able to develop structures that can resist nature’s most difficult loads, including earthquakes,” said Tom D’Arcy, spokesman for the Precast/Prestressed Institute and chairman of The Consulting Engineers Group, Inc.
The $2.3 million research project is a collaboration between UC San Diego, the University of Arizona and Lehigh University. It is funded by the Precast/Prestressed Concrete Institute and its member companies and organizations, the National Science Foundation, the Charles Pankow Foundation and the Network for Earthquake Engineering Simulation (NEES).
During the tests, the researchers simulated earthquakes for different regions of the country, including Berkeley, Calif..; Knoxville, Tenn; and Seattle, Wash.
“We conducted tests from lower seismicity all the way to higher seismicity and shook the building stronger and stronger each time with a higher intensity,” Restrepo said.
The results of the research are expected to be implemented into building codes across the United States within the next few years. The researchers and industry leaders hope that this project and others like it will help prevent the future failure of buildings, much like what happened during the 6.7 magnitude earthquake in Northridge, CA. in 1994, with the collapse of several precast parking structures.
“Since that time, we have been working to come up with designs that will make these structures survive a Northridge earthquake or stronger,” said Robert Fleischman, principal investigator of the project and a civil engineering professor at the University of Arizona.
Seismic Simulation
Before the testing, the researchers performed computer simulations to help design the three-story structure and to determine where sensors should be placed on it. The data recorded by the sensors were used to take measurements of certain physical phenomena on the structure such as displacements, strains, and accelerations caused by the shaking; and to estimate forces in the structure. The data collected will also explain behavior of the structure during and after jolts, and will be used to compare directly to the simulations to either validate or adjust the computer models.
The use of these sensors, along with the computer simulation, may help lower costs of future seismic tests.
“We are only able to perform physical experiments on that one structure, but if we can show that our models capture important response properly, we can run hundreds of earthquake simulations a year for the cost of a graduate student, a fast computer and a software license, which, at around $50,000, is substantially less than the costs of these kinds of tests,” Fleischman said, adding that the researchers hope to have their first formal report on the seismic tests completed by early 2009.
The $9 million Englekirk shake table is one of 15 earthquake testing facilities. The UCSD-NEES shake table, the largest in the United States and the only outdoor shake table in the world, is ideally suited for testing tall, full-scale buildings.
“The Englekirk Center is very important to the research community and to the industry because it has an outdoor environment where we can perform large scale tests that can’t be done anywhere else in the world,” Restrepo said.
The recent seismic tests are an example of how the Jacobs School is performing research at the forefront of the National Academy of Engineering’s Grand Challenges for Engineering in the 21st Century.

Source: http://www.sciencedaily.com/releases/2008/08/080822131253.htm

Earth cracks in UP seismic related: Expert

Motion of a massive granitic body under the earth could be the probable reason behind alarming cracks on the earth crust that have created a panic like situation in northern Indian state of Uttar Pradesh (UP).
“If this granitic craton motion is changed due to some tectonic reason, one may see subsidence at large scale—since a fault is present along Kanpur-Lucknow—there could be danger of large surface deformation,” cautioned an US based Indian scientist Ramesh Singh.
The effect of motion of this block will be reflected in widespread cracks, he said. Singh is a Professor at George Mason University in Washington and vice chair of GeoRisk Commission of the International Union of Geodesy and Geophysics.
He further said that the Government of India should monitor seismic activities in the area to avert any major disaster due to this motion.
Singh, who had extensively studied the seismology in this part of UP during his stint at IIT Kanpur as a Professor said if the orientation of such long cracks was in the east-west direction, then the cracks could be due to stress on the surface of the earth due to motion of this massive craton (granitic body) exposed near Jhansi.
He said this massive body underlying the region is inclined towards northeast with depth reaching 300-500 metres near Kanpur and 1,200 metres in Lucknow.
About 18 months back, scientists observed a shift in the position of the Sangam—the confluence of rivers Ganges and Yamuna and mythical Saraswati near Allahabad—and thought it was due to the sediment load in the rivers or due to plate motion, Singh said.
“Now, the appearance of large widespread cracks is clear evidence of neo-tectonic activities associated with the building of stress in this region and we must monitor seismic activities along Kanpur-Lucknow and Moradabad faultlines,” the Professor said.
Singh said he initially suspected that the cracks might be due to subsidence as a result of excessive groundwater withdrawal but ruled it “since the cracks were seen on a regional scale in many parts of Kanpur, Hamirpur, and Allahabad.”
The formation of cracks on the earth continues to affect various districts of UP and two villages near Lucknow are the latest to witness long fissures on the surface.
Fields in Kakori block’s two villages, Dullu Khera and Vader Khera, about 10 km from Lucknow, have developed wide cracks up to 250 metres long, officials said.
Besides the villages in Lucknow district, six districts of Uttar Pradesh have been witnessing this phenomenon for about a week.

Source: http://www.igovernment.in/site/earth-cracks-in-up-seismic-related-expert/

Active Submarine Volcanoes Found Near Fiji

ScienceDaily (June 20, 2008) — Several huge active submarine volcanoes, spreading ridges and rift zones have been discovered northeast of Fiji by a team of Australian and American scientists aboard the Marine National Facility Research Vessel, Southern Surveyor.

On the hunt for subsea volcanic and hot-spring activity, the team of geologists located the volcanoes while mapping previously uncharted areas. Using high-tech multi-beam sonar mapping equipment, digital images of the seafloor revealed the formerly unknown features.
The summits of two of the volcanoes, named ’Dugong’, and ’Lobster’, are dominated by large calderas at depths of 1100 and 1500 metres.
During the six-week research expedition in the Pacific Ocean, scientists from The Australian National University (ANU), CSIRO Exploration & Mining and the USA, collaborated to survey the topography of the seafloor, analysing rock types and formation, and monitoring deep-sea hot spring activity around an area known as the North Lau Basin, 400 kilometres northeast of Fiji.
The voyage’s Chief Scientist, ANU Professor Richard Arculus describes the terrain – the result of extreme volcanic and tectonic activity – as spectacular. “Some of the features look like the volcanic blisters seen on the surface of Venus,” he says.
“These active volcanoes are modern day evidence of mineral deposition such as copper, zinc, and lead and give an insight into the geological make-up of Australia,” he says.
“It provides a model of what happened millions of years ago to explain the formation of the deposits of precious minerals that are currently exploited at places like Broken Hill and Mt Isa. It may also provide exploration geologists with clues about new undiscovered mineral deposits in Australia.
“These deep-sea features are important in understanding the influences that have shaped not only our unique continent but indeed the whole planet,” Professor Arculus says.
Such discoveries highlighted man’s lack of knowledge about the world’s oceans. “We know more about the surface of Mars than we know about the ocean seafloor,” Professor Arculus says.
CSIRO’s Director of Research Vessels, Captain Fred Stein, says the expedition was a humbling experience. “It was a reminder that at the beginning of the 21st century it is still possible – on what is often regarded as a thoroughly explored planet – to discover a previously unknown massif larger than Mt Kosciuszko,” he says.
“We are fortunate that we can offer the scientific capability of the Southern Surveyor to Australian scientists. It’s the only Australian research vessel that can provide the opportunity to conduct such valuable research to make these kinds of discoveries possible.”

Source: http://www.sciencedaily.com/releases/2008/06/080619093259.htm

Chinese scientists call for better quake prediction

BEIJING] Scientists in China are calling for improvements in earthquake prediction, including the establishment of an early-warning system and methods for scientists to share quake information.
The calls come after the Sichuan earthquake — the country's most serious earthquake in 30 years — hit on 12 May (see China displays openness in earthquake response).
Ni Sidao, a professor of geophysics at the University of Science and Technology of China, says that although current scientific methods cannot accurately predict an earthquake, an early-warning system could alert people to leave for open spaces before buildings are destroyed.
Ni made his remarks last week (25 May) alongside other scientists at the China Science and Humanities Forum in Beijing, operated by the Graduate University of the Chinese Academy of Sciences.
He said that P waves — early-arriving non-destructive seismic waves — can be used to detect and calculate the scale of an earthquake within ten seconds with the aid of computers.
In the case of Sichuan, the later-arriving, destructive seismic waves (S waves) took 30 seconds to reach Beichuan — the most seriously hit county, 90 kilometres north of the epicentre — and nearly 100 seconds to reach Qingchuan County, 200 kilometres from the epicentre.
People in Beichuan could have had a ten-second warning of the earthquake with an early-warning system, allowing some to move outdoors and trains to stop to avoid derailing, said Ni.
But he admitted that current seismic monitoring stations in most parts of China are too isolated to form a warning network.
Ren Luchuan, a senior researcher at China Earthquake Networks Centre (CENC), welcomes Ni's suggestions, but says such a system is very difficult to operate.
"[The time difference between P and S waves] is so short that it is very hard to establish a system to notify residents," he told SciDev.Net, though he says such a system could be used for key sites such as nuclear power stations, which could close reactors.
Longer-term prediction seems to be just as fraught with problems.
In the latest issue of the Chinese language journal Science and Technology Review (28 May), Wu Lixin from the Chinese University of Mining and Technology, Beijing, and colleagues report an abnormal temperature rise in the thermal satellite images of the eastern front of Qinghai–Tibet plateau — the fault that caused the earthquake — 20 days before the Sichuan earthquake.
The authors suggested this rise could be caused by tectonic plate movement, and could be an indicator for earthquake prediction.
But Ren says many factors could cause the abnormal temperature increases, leading to uncertainty in using temperature change to predict earthquakes.
In a separate article published in the same issue, however, Wu writes that there should be more intensive, accurate and consistent analyses of thermal satellite images, and that these should be frequently checked against seismic wave monitoring.
In addition, Wu says an earthquake information sharing system should be established, so that general researchers can analyse or input data about abnormal observations into a system for professional seismologists to screen.

Source : http://www.scidev.net/en/news/chinese-scientists-call-for-better-quake-predictio.html

Earthquake In Illinois Could Portend An Emerging Threat

ScienceDaily (Apr. 25, 2008) — To the surprise of many, the earthquake on April 18, 2008, about 120 miles east of St. Louis, originated in the Wabash Valley Fault and not the better-known and more-dreaded New Madrid Fault in Missouri's bootheel.

The concern of Douglas Wiens, Ph.D., and Michael Wysession, Ph.D., seismologists at Washington University in St. Louis, is that the New Madrid Fault may have seen its day and the Wabash Fault is the new kid on the block.
The earthquake registered 5.2 on the Richter scale and hit at 4:40 a.m. with a strong aftershock occurring at approximately 10:15 a.m. that morning, followed by lesser ones in subsequent days. The initial earthquake was felt in parts of 16 states.
"I think everyone's interested in the Wabash Valley Fault because a lot of the attention has been on the New Madrid Fault, but the Wabash Valley Fault could be the more dangerous one, at least for St. Louis and Illinois," said Wiens, professor of earth and planetary sciences in Arts & Sciences. "The strongest earthquakes in the last few years have come from the Wabash Valley Fault, which needs more investigation."
Wiens said that seismologist Robert Hermann of Saint Louis University, Gary Pavils of Indiana University, and several geologists including Steven Obermeir of the U.S. Geological Survey (USGS), have made studies of the Wabash Valley Fault. Pavils also has run a dense local array of stations and recorded many very small earthquakes at the Wabash Valley Fault. Hermann has studied the 1968 magnitude 5.5 earthquake, the largest ever recorded there. Obermeir and others have found disturbed sediments from previous earthquakes along the fault with estimated magnitudes of about 7 on the Richter scale over the past several thousand years.
According to Wysession, there are 200,000 earthquakes recorded every year, with a magnitude 6 earthquake happening every three days somewhere in the world.
"There hasn't been a magnitude 6 earthquake on the New Madrid zone in more than 100 years, yet in 20 years there have been three magnitude 5 or better earthquakes on the Wabash Valley Fault," said Wyssession, associate professor of earth and planetary sciences. "There is evidence that sometime in the past the Wabash Valley Fault has produced as strong as magnitude 7 earthquakes. On the other hand, the New Madrid Fault has been very quiet for a long time now. Clearly, the Wabash Valley Fault has gotten our deserved attention."
Wysession said a recent re-analysis of data by USGS shows that the New Madrid fault risk is much less than was thought three decades ago. The three notable earthquakes that occurred at the end of 1811 and the beginning of 1812 were not magnitude 8s, rather magnitude 7s. A magnitude 8 is 30 times more energetic than a magnitude 7.
"The damage to the region by those earthquakes has been exaggerated," Wysession said. "St. Louis was here at the time, and all that happened was some chimneys fell in East St. Louis. The little village of St. Genevieve, closer to the fault zone, had no damage at all. But, let's face it, St. Louis is the biggest city in the region of both faults, and the Wabash Valley Fault is closer to us. If the big one does occur, it's looking more like it will come out of Illinois."
Wysession said that the North American Earth's crust is filled with cracks and faults, and that an earthquake can occur anywhere on the continent. Many of the faults are undetected.
"As the continents bang into each other, sometimes they pull apart, and the crust cracks and ruptures, causing earthquakes," he explained. "This whole region of New Madrid and the Wabash Valley seismic zone became a rift zone about 750 million years ago when the continent almost broke apart. There was a lot of volcanic activity, a lot of seismic activity. The crust got stretched and thinned. By looking at seismometers, we can actually see many of these faults in the thinning of crusts underground."
Wysession said that an earthquake in the Midwest will be felt ten times farther away than one occurring in the western United States because the crust beneath the Midwest is very old, stiff and cold. The rock is about 1.7 billion years old and the seismic waves can travel very long distances through this type of crust. It can be felt hundreds of miles away, even if it was a smaller earthquake. In the western United States, the rock is hotter, and thus it dampens the shock waves and they are not felt as far away.
Despite the fact that most seismologists, including Wysession and Wiens, don't think it likely that earthquakes ever will be predicted — which inevitably dredges up memories of the 1990 Midwest earthquake scare sparked by Iben Browning — Wysession says that there are some precursory phenomena that have been observed right before some earthquakes. Radon or helium gas may leak out of the ground as the ground cracks. Sometimes water well pressure changes, or there's a change in the magnetic field. Electrical resistivity changes have been noted, too.
"These are changes we can measure with instruments, but we can't sense them as humans," he said. "Many people think that animals sense atmospheric changes. You always get stories about Rover going bananas right before an earthquake. But until Rover learns to tell us what he's barking about, we won't be able to employ animals in any predictive way. "

Source:http://www.sciencedaily.com/releases/2008/04/080424171350.htm

Satellite data reveals seismic link to volcanoes

Local earthquakes boost volcanic activity in Indonesia, researchers have shown using satellite data. The finding could, they say, point to a predictive role for satellite imaging.
Volcanic activity in two ongoing eruptions, Merapi and Semeru on the Indonesian island of Java, increased following a local earthquake in May 2006 that measured 6.4 on the Richter scale. The flare-up began three days after the earthquake and lasted for nine days.
The researchers, led by Andrew Harris of the University of Hawaii, used thermal imaging data from an instrument on a NASA (the US National Aeronautics and Space Administration) satellite.
This provides near real-time data on global hotspots such as volcanic eruptions and wildfires. The team used data from a 35 day period, including the time of the earthquake.
"We found clear evidence that the earthquake caused both volcanoes to release greater amounts of heat, and lava emission surged to two to three times higher than prior to the tremor," Harris told NASA.
The researchers believe that the changes in eruption were due to seismic waves from the earthquake travelling to the area round the volcano and triggering an increased flow of molten rock.
But Dave Rothery, a vulcanologist in the Department of Earth Sciences at the UK-based Open University, warned that the study’s focus — one earthquake stimulating two volcanoes — could be a coincidence and more examples are needed.
The researchers say the work shows that satellite imaging could play a predictive role in eruptions, ultimately alerting people living near volcanoes to increased volcanic activity.
"I'm not sure we're up to early warning yet," Harris told SciDev.Net. "But immediately once an eruption begins we can detect its thermal signature, post its location on our global map, and perhaps alert people via automated email."
Rothery added that anyone with internet access could identify when volcanic activity is increasing in their area, information which could be "factored into decisions about evacuation".
The research was published in Geophysical Research Letters.

Source:

http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=3553&language=1

Deadly tremors that strike without warning- Facts About Earthquakes

Every day an earthquake happens somewhere in the world. Many are so light that they cannot be detected. On average just 100 quakes cause damage out of the estimated 1.4 million earthquakes that occur every year.
Scientists cannot predict when an earthquake will strike, but they have been able to map where earthquakes are most likely to happen.
Most of the largest earthquakes occur within the Pacific "Ring of Fire", a horseshoe-shaped band of volcanoes and fault lines circling the edges of the Pacific Ocean.
Tsunami are large water waves typically generated by underwater earthquakes or landslides triggered by seismic activity.
KEY FACTS:
The largest recorded earthquake in the world was magnitude 9.5 in Chile, May 22, 1960.
Most earthquakes occur at depths of less than 80 km (50 miles) from the Earth's surface.
The world's deadliest recorded earthquake occurred in 1556 in central China, where most people lived in caves carved from soft rock. An estimated 830,000 people died.
The earliest recorded evidence of an earthquake dates back to 1831 BC in China's Shandong province.
Source: The U.S. Geological Survey's Earthquake Facts page.

Study helps predict big Mediterranean quake

LONDON, March 9 (Reuters) - Scientists have found evidence that an overlooked fault in the eastern Mediterranean is likely to produce an earthquake and tsunami every 800 years as powerful as the one that destroyed Alexandria in AD 365.
Using radiocarbon dating techniques, simulations and computer models, the researchers recreated the ancient disaster in order to identify the responsible fault, they said in a study published in the journal Nature Geoscience on Sunday.
"We are saying there is probably a repeat time of 800 years for this kind of earthquake," said Beth Shaw, a seismologist at the University of Cambridge, who led the study.
Scientists study past earthquakes in order to determine the future likelihood of similar large shocks. Identifying the fault for the AD 365 earthquake and tsunami is important for the tens of millions of people in the region, Shaw said.
The fault close to the southwest coast of Crete last produced a big enough quake to generate a tsunami about 1300, which means the next powerful one could come in the next 100 years, she added in a telephone interview.
Shaw and her colleagues calculate the likely intervals by measuring the motion of either side of the fault to gauge how often such large earthquakes would have to occur to account for that level of motion, she said.
Their computer model suggested an 8 magnitude quake on the fault would produce a tsunami that inundates the coastal regions of Alexandria and North Africa, the southern coast of Greece and Sicily all the way up the Adriatic to Dubrovnik, Shaw said.
This would be similar to the ancient quake in AD 365 that caused widespread destruction in much of Greece and unleashed a tsunami that flooded Alexandria and the Nile Delta, likely killing tens of thousands of people, she said.
"This is consistent with the historical record of the tsunami," she said. (Reporting by Michael Kahn; Editing by Janet Lawrence)

Source: http://www.alertnet.org/thenews/newsdesk/L07804229.htm

Quake jolts UK, damages to property worth 10 mn pounds

Britain was on wednesday jolted by an earthquake, the biggest to hit the country in nearly 25 years that damaged property worth over 10 million pounds. The tremor, measuring 5.2 on the Richter scale, hit shortly before 1:00 am (0630 IST) with its epicentre in Lincolnshire, but people were woken as far away as Wales, Scotland and Yorkshire. One person narrowly escaped death when a chimney smashed through the roof of his terraced home and crashed into his bedroom in Wombwell in South Yorkshire. The Association of British Insurers said that the cost of damage to homes and property is likely to be in excess of 10 million pounds.

The British Geological Survey (BGS) initially gave the magnitude for the 12.56 am earthquake as 5.3 on the Richter scale but has now said it was closer to 5.2. It said the epicentre was eight km east of Market Rasen, Lincolnshire, and 22 km south west of Grimsby. The tremor is the biggest in Britain since 1984 when north Wales was hit by a quake which was registered at 5.4 on the Richter scale. "There is slight structural damage, cracks and a couple of chimneys damaged. There's nothing serious at present. "Mostly people were distressed by it so there were a large quantity of calls coming in."

The police in the Midlands received more than 5,000 calls in an hour and in Dudley, 12 people walked into the local police station in their pyjamas.

The BGS said it records around 200 earthquakes in the UK each year - an eighth of which are able to be felt by residents. Buildings are deemed to be at risk from earthquakes above 5 on the Richter Scale, according to the Environment Agency.

The United States Geological Survey claimed that while the event was "light to moderate" on a world scale, it was "very significant", given the UK's relatively uneventful seismic history. Rafael Abreu, a geophysicist at the USGS National Earthquake Information Service, said: "It was a light to moderate event in relation to what has happened in Indonesia recently. But what is interesting about this event is that it was in an area where you would not expect it. "In an seismic area like this it is very significant. The UK usually has minor activity -- it's not particularly seismic."

The largest earthquake recorded in the UK was about 120 km from north east of Great Yarmouth in the North Sea on June 7, 1931. It measured 6.1 and was felt across Britain, in eastern Ireland, Belgium, the Netherlands, and parts of Germany, France, Norway and Denmark. People in Newcastle, Yorkshire, Manchester, the Midlands and Norfolk and also parts of Wales, felt the tremor. Seismologist Dr Brian Baptie of the BGS said: "This is a significant earthquake for the UK and will have been widely felt across England and Wales." A Lincolnshire police spokeswoman said the force had received dozens of calls from residents.

Sources : PTI

Earth's Getting 'Soft' In The Middle, Geologists Note

ScienceDaily (Jan. 28, 2008) — A new study suggests that material in part of the lower mantle has unusual electronic characteristics that make sound propagate more slowly, suggesting that the material there is softer than previously thought. The results call into question the traditional techniques for understanding this region of the planet.

Since we can't sample the deepest regions of the Earth, scientists watch the velocity of seismic waves as they travel through the planet to determine the composition and density of that material. Now a new study suggests that material in part of the lower mantle has unusual electronic characteristics that make sound propagate more slowly, suggesting that the material there is softer than previously thought. The results call into question the traditional techniques for understanding this region of the planet.
The lower mantle extends from about 400 miles to 1800 miles (660-2900 kilometers) into Earth and sits atop the outer core. Pressures and temperatures are so brutal there that materials are changed into forms that don't exist in rocks at the planet's surface and must be studied under carefully controlled conditions in the laboratory. The pressures range from 230,000 times the atmospheric pressure at sea level (23 GPa), to 1.35 million times sea-level pressure (135 GPa). And the heat is equally extreme--from about 2,800 to 6,700 degrees Fahrenheit (1800K--4000K).
Iron is abundant in the Earth, and is a major component of the minerals ferropericlase and the silicate perovskite in the lower mantle. In previous work, researchers found that the outermost electrons of iron in ferropericlase are forced to pair up under the extreme pressures creating a so-called spin-transition zone within the lower mantle.
"What happens when unpaired electrons--called a high-spin state--are forced to pair up is that they transition to what is called a low-spin state. And when that happens, the conductivity, density, and chemical properties change," explained Goncharov. "What's most important for seismology is the acoustic properties--the propagation of sound. We determined the elasticity of ferropericlase through the pressure-induced high-spin to low-spin transition. We did this by measuring the velocity of acoustic waves propagating in different directions in a single crystal of the material and found that over an extended pressure range (from about 395,000 to 590,000 atmospheres) the material became 'softer'--that is, the waves slowed down more than expected from previous work. Thus, at high temperature corresponding distributions will become very broad, which will result in a wide range of depth having subtly anomalous properties that perhaps extend through most of the lower mantle."
The results suggest that scientists may have to go back to the drawing board to model this region of the Earth.
The authors, including Alexander Goncharov from the Carnegie Institution's Geophysical Laboratory, present their results in the January 25, 2008, issue of Science.
This research was partly funded by Carnegie Institution of Washington, the National Science Foundation and the U.S. Department of Energy/National Nuclear Security Agency through the Carnegie/DOE Alliance Center' and the W. M. Keck Foundation.
Adapted from materials provided by Carnegie Institution.

Source: http://www.sciencedaily.com/releases/2008/01/080124145022.htm

First Evidence Of Under-ice Volcanic Eruption In Antarctica

ScienceDaily (Jan. 22, 2008) — The first evidence of a volcanic eruption from beneath Antarctica's most rapidly changing ice sheet has been reported. The volcano on the West Antarctic Ice Sheet erupted 2000 years ago (325BC) and remains active.

The subglacial volcano has a 'volcanic explosion index' of around 3-4. Heat from the volcano creates melt-water that lubricates the base of the ice sheet and increases the flow towards the sea. Pine Island Glacier on the West Antarctic Ice Sheet is showing rapid change and BAS scientists are part of an international research effort to understand this change.
Using airborne ice-sounding radar, scientists from British Antarctic Survey (BAS) discovered a layer of ash produced by a 'subglacial' volcano. It extends across an area larger than Wales.
Lead author* Hugh Corr of the BAS says, "The discovery of a 'subglacial' volcanic eruption from beneath the Antarctic ice sheet is unique in itself. But our techniques also allow us to put a date on the eruption, determine how powerful it was and map out the area where ash fell. We believe this was the biggest eruption in Antarctica during the last 10,000 years. It blew a substantial hole in the ice sheet, and generated a plume of ash and gas that rose around 12 km into air."
The discovery is another vital piece of evidence that will help determine the future of the West Antarctic Ice Sheet and refine predictions of future sea-level rise. Glaciers are like massive rivers of ice that flow towards the coast and discharge icebergs into the sea.
Co-author Professor David Vaughan (BAS) says,"This eruption occurred close to Pine Island Glacier on the West Antarctic Ice Sheet. The flow of this glacier towards the coast has speeded up in recent decades and it may be possible that heat from the volcano has caused some of that acceleration. However, it cannot explain the more widespread thinning of West Antarctic glaciers that together are contributing nearly 0.2mm per year to sea-level rise. This wider change most probably has its origin in warming ocean waters."
About the volcano
The volcano is located beneath the West Antarctic ice sheet in the Hudson Mountains at latitude 74.6°South, longitude 97°West. Volcanoes are an important component of the Antarctic region. They formed in diverse tectonic settings, mainly as a result of mantle plumes acting on the stationary Antarctic plate. The region also includes amongst the world's best examples of a long-lived continental margin arc (Antarctic Peninsula), a very young marginal basin (Bransfield Strait) and an oceanic island arc (South Sandwich Islands). Many extinct volcanoes are very well preserved and others are still active (e.g. Deception Island, Mount Erebus, and the South Sandwich Islands).
Volcanic eruptions were common during the past 25 million years, and coincided with the great period of climatic deterioration that resulted in the formation of the Antarctic ice sheet. Many of the volcanoes show the effects of interaction with ice. BAS has played a major role in describing these effects and modelling their influences on the resulting volcanic sequences. It is important to describe and understand these interactions in geologically recent times in order to predict future configurations of the ice sheet and its role in the global system.
*The paper 'A recent volcanic eruption beneath the West Antarctic ice sheet' by Hugh F Corr and David G Vaughan is published in the February edition of Nature Geosciences (online).
Adapted from materials provided by British Antarctic Survey.

Source: http://www.sciencedaily.com/releases/2008/01/080120160720.htm

'Ultrasound' Of Earth's Crust Reveals Inner Workings Of A Tsunami Factory

ScienceDaily (Nov. 15, 2007) — Research just announced by a team of U.S. and Japanese geoscientists may help explain why part of the seafloor near the southwest coast of Japan is particularly good at generating devastating tsunamis, such as the 1944 Tonankai event, which killed at least 1,200 people. The findings will help scientists assess the risk of giant tsunamis in other regions of the world.

Geoscientists from The University of Texas at Austin and colleagues used a commercial ship to collect three-dimensional seismic data that reveals the structure of Earth's crust below a region of the Pacific seafloor known as the Nankai Trough. The resulting images are akin to ultrasounds of the human body. The results, published in the journal Science, address a long standing mystery as to why earthquakes below some parts of the seafloor trigger large tsunamis while earthquakes in other regions do not. The 3D seismic images allowed the researchers to reconstruct how layers of rock and sediment have cracked and shifted over time. They found two things that contribute to big tsunamis.

First, they confirmed the existence of a major fault that runs from a region known to unleash earthquakes about 10 kilometers (6 miles) deep right up to the seafloor. When an earthquake happens, the fault allows it to reach up and move the seafloor up or down, carrying a column of water with it and setting up a series of tsunami waves that spread outward.

Second, and most surprising, the team discovered that the recent fault activity, probably including the slip that caused the 1944 event, has shifted to landward branches of the fault, becoming shallower and steeper than it was in the past. "That leads to more direct displacement of the seafloor and a larger vertical component of seafloor displacement that is more effective in generating tsunamis," said Nathan Bangs, senior research scientist at the Institute for Geophysics at The University of Texas at Austin who was co-principal investigator on the research project and co-author on the Science article.

The Nankai Trough is in a subduction zone, an area where two tectonic plates are colliding, pushing one plate down below the other. The grinding of one plate over the other in subduction zones leads to some of the world's largest earthquakes.

In 2002, a team of researchers led by Jin-Oh Park at Japan Marine Science and Technology Center (JAMSTEC) had identified the fault, known as a megathrust or megasplay fault, using less detailed two-dimensional geophysical methods. Based on its location, they suggested a possible link to the 1944 event, but they were unable to determine where faulting has been recently active. "What we can now say is that slip has very recently propagated up to or near to the seafloor, and slip along these thrusts most likely caused the large tsunami during the 1944 Tonankai 8.1 magnitude event," said Bangs. The images produced in this project will be used by scientists in the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), an international effort designed to, for the first time, "drill, sample and instrument the earthquake-causing, or seismogenic portion of Earth's crust, where violent, large-scale earthquakes have occurred repeatedly throughout history." "The ultimate goal is to understand what's happening at different margins," said Bangs. "The 2004 Indonesian tsunami was a big surprise. It's still not clear why that earthquake created such a large tsunami. By understanding places like Nankai, we'll have more information and a better approach to looking at other places to determine whether they have potential. And we'll be less surprised in the future."
Bangs' co-principal investigator was Gregory Moore at JAMSTEC in Yokohama and the University of Hawaii, Honolulu. The other co-authors are Emily Pangborn at the Institute for Geophysics at The University of Texas at Austin, Asahiko Taira and Shin'ichi Kuramoto at JAMSTEC and Harold Tobin at the University of Wisconsin, Madison. Funding for the project was provided by the National Science Foundation, Ocean Drilling Program and Japanese Ministry of Education, Culture, Sports and Technology.

Source: http://www.sciencedaily.com/releases/2007/11/071115164101.htm

Israeli quake may be precursor to disaster

Israeli quake may be precursor to disaster
JERUSALEM, Oct. 14 (UPI) -- A 3.0-magnitude earthquake that rattled Israel Sunday may be a precursor to a much larger quake scientists have predicted for the region.
While Sunday's earthquake in Israel's Jordan rift valley area was minor, as were two other recent temblors in the region, scientists are concerned a larger quake could occur due to a nearby rift, Ynetnews reported.
The Syrian-African rift, known for being volatile, is close to the valley area and therefore the site of the recent earthquakes.
Department of Environmental Sciences and Geophysics scientist Shmuel Marko and Oded Katz of the Geophysical Institute of Israel said in a recent study that such seismic activity appears to indicate a more disastrous quake is imminent.
"We know that the area between the Kinneret and the Dead Sea was subject to several large quakes, in 31 B.C., 362 B.C., 749 B.C. and 1033 A.D.," the pair said in that study. "Another major one is coming soon."

Does Underground Water Regulate Earthquakes?

Does Underground Water Regulate Earthquakes?
Science Daily — Earthquakes happen to be surface (shallow-focus), intermediate and deep ones. Seismologists mark out the boundary between the first two types at the depth of about 70 kilometers, its nature being still unclear.

Russian researchers, specialists of the Institute of Maritime Geology and Geophysics (Far-Eastern Branch, Russian Academy of Sciences), Geophysical Center of the Russian Academy of Sciences and the P.P. Shirshov Institute of Oceanology (Russian Academy of Sciences) have put forward a hypothesis that the seismic boundary is simultaneously the lower boundary of hydrosphere. The earthquakes character depends on underground water.
Earthquakes taking place “at different sides of the boundary” differ from each other not only by the depth. Shallow-focus earthquakes – they account for about 85% of all recorded events - often take place under the influence of periodic external effects, for example, rising tides, which disturb the entire lithosphere of the Earth. Periodicity is not inherent to deeper earthquakes, they always occur by chance. The conclusion was made by the researchers who had analyzed the world ISC/NEIC catalogues data that covers the 1964-2005 period and takes into account about 80,000 events.
Seismologists connect existence of the 70-kilometer boundary with water state changes in the interior of the Earth. The deeper the water molecules are located, the more compressed they are. At the depth of about 70 kilometers, the water compression strain index increases up to 1.3. This is the way water molecules are squeezed in the crystal lattice. Above this boundary, water exists mainly in free phase, below the boundary – water embeds into the rock crystallite composition.
The rock containing free water (above the boundary) promptly reacts to periodic tidal effects, even the faintest ones. Pressure changes and respective environment density changes cause formation of a crack system, where free water rushes to. The cracks widen, increase, and rock decay gives birth to a seismic focus. In the rock, where free water is absent (below the boundary), weak tidal effects are not accumulated and deformation does not grow.
So, the seismic boundary at the depth of about 70 kilometers (where, according to the researchers’ assumption, the lower hydrosphere boundary runs) separates the events that are able to react to external action and the ones incapable of such reaction. Therefore, this boundary separates different types of earthquakes. However, it is still a hypothesis that requires experimental validation.
Note: This story has been adapted from material provided by Russian Academy Of Sciences.

Source: http://www.sciencedaily.com/releases/2007/09/070915105639.htm