The spectre of New Madrid

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Who Knew Ill. Is Hotbed of Seismic Activity?

Scientists Not Surprised at Midwest Quake
April 18, 2008 - Southern Illinois a Hotbed of Earthquake Activity, Experts Say

As the nation marveled over a rare magnitude 5.2 earthquake that startled Illinois residents early this morning, earthquake experts weren't all that surprised by the temblor, they told ABCNEWS.com. The earthquake struck southern Illinois about six miles north of Mount Carmel, at 4:37 a.m., violently shaking people from their beds, swaying Chicago skyscrapers and vibrating the earth as far east as Georgia. As the morning wore on, at least two significant aftershocks rocked the Midwest.

Astonished messages from Midwesterners flew across sites such as Twitter.com about the aftershocks seconds after they were felt, even before the U.S. Geological Survey reported them, and Verizon customers placed three times more calls than normal between 4 a.m. and 5 a.m. Scientists say the earthquake likely took place on the Wabash Valley fault system, which is in the southern parts of Illinois and Indiana and is near but not related to the larger and more volatile New Madrid fault, which extends farther south.

Although today's quake was felt hundreds of miles away, so far no injuries or major damage were reported. Despite the nation's shock at the quake, according to experts the Midwest has long been a hotbed of seismic activity. "Southern Illinois has had earthquakes of this size throughout history," said Nano Seeber, a senior research scientist at the Lamont-Doherty Earth Observatory at Columbia University. "Is this an earthquake zone? Yes."

More ABC News: Who Knew Ill. Is Hotbed of Seismic Activity?

See also:

Update: Strong Aftershock Felt In Midwest
April 18, 2008 - Several aftershocks have been registered following a 5.2 magnitude earthquake that shook the Midwest early Friday morning.

One of the aftershocks was quite strong, at 4.6 on the Richter scale, according to U.S. Geological Survey geophysicist Angel Gutierrez. It occurred 10:15 a.m. The number of aftershocks observed ranged from 6 to 12, with lesser magnitudes ranging from 2.2 to 2.5. The first tremor, 5.2 on the Richter scale, hit the Midwest at 4:36 a.m., near West Salem town, 60 miles northwest of Evansville in Indiana.

Even with the aftershocks, there were still no reports of any injuries or damage caused by the dawn temblor, except for a crack on U.S. Route 51 near Cairo, according to Mike Claffey, a spokesman for Illinois' Department of Transportation. State crew are going around major thoroughfares checking roads and bridges for earthquake-related damage.

The last tremor that rocked the Midwest with a similar strength was a 5.0 earthquake in 2002.

Update: Strong Aftershock Felt In Midwest | April 19, 2008 | AHN

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A Little Bit of Shakin' Going On....

Is the Earth Any Shakier Than Usual?
May 7, 2008 - U.S. Earthquakes Jangle Nerves, Leave Scientists With Questions; Even "micro" quakes around U.S. set nerves on edge.

It was only a magnitude 1.8 on the scale geologists use. But its center was just a mile from Annandale, Va., in the suburbs of Washington, D.C. — enough to get the attention of scientists and local emergency officials. It happened on Tuesday afternoon, and though it did no damage, hundreds of people called local news outlets saying they had heard a bang and felt a mild jolt. "Of course, this was a very small earthquake, but we've had larger ones in this part of the country in the past," said Leonardo Seeber, senior research scientist at the Lamont-Doherty Earth Observatory of Columbia University in Palisades, N.Y.

Several others have made news lately: The normally quiet area around Reno, Nev., has had dozens of tremors since late April, the largest measuring 4.7. Southern Illinois had one on April 18, measuring 5.2. And there was one on April 30 in northern California, about 190 miles north of Sacramento, with a magnitude of 5.4. What's going on? Nothing unusual, say scientists — unless the shaking is going on under your feet.

An Earthquake? In Virginia?

Virginia, like most of the world, is geologically stable. There hasn't been much seismic activity in the Washington suburbs since 1997, and the quake that happened then only had a magnitude of 2.5. Below the level of 3.0, scientists refer to tremors as "microquakes," and say it's unusual for people to feel them. About a thousand of them happen somewhere on the planet every day.

"Quakes of this size are strong enough to be felt in dense population areas, especially in high-rise buildings," said Bruce Presgrave, a geophysicist with the U.S. Geological Survey in Golden, Colo., in an interview with the Associated Press. Scientists say something of magnitude 5 is a "moderate" earthquake. A magnitude 4 is "light." A 3 is "minor" and below that is "micro."

More ABC News: Is the Earth Any Shakier Than Usual?

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China quake a preview of the big one for Calif.?...

China quake seen as 'worst case' for California
Tues., May. 13, 2008 - Seismologists fear deadly devastation could occur in the Los Angeles area

The deadly earthquake in China this week was devastating and felt across a vast area. The epicenter struck central China's Sichuan Province, yet it was felt as far away as Taiwan, Thailand and Vietnam. And its origin was shallow. In short, it is exactly what seismologists fear could happen in Southern California some day.

Scientists think the Sichuan earthquake was caused by seismic activity associated with the Indian land-mass colliding with the Asian continent (this same force has slowly built up the Himalaya mountain range). Because this week's temblor was relatively shallow — 11.8 miles (19 km) below the ground — it caused especially violent quaking on the surface, which led to extensive damage.

"Some of our worst-case scenarios would involve an earthquake somewhat like this on one of the faults that run through the L.A. region," said Thomas Heaton, a professor of engineering seismology at Caltech. "If we had one like this, it would be a tremendous natural disaster. We would expect to have extensive damage in the several hundred-billion dollar range."

China's shaky past

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Earthquake domino effect theory...

Can big earthquakes trigger a domino effect?
Sun., May. 25, 2008 - Shakers can set off shaking in other parts of the world, new research shows

The giant earthquake that unleashed the Indian Ocean tsunamis in 2004 — killing more than 225,000 people in one of the deadliest natural disasters in history — might also have triggered other quakes around the world, new findings reveal. The earthquake that ravaged China last week may also have set off other quakes around the globe, but that data has not been analyzed yet. But the new research shows that major earthquakes may routinely set off smaller jolts, even on the opposite side of the planet and in areas not prone to quakes.

Earthquakes rank among the most destructive events on the planet. The 2004 Indian Ocean quake was magnitude 9.3, unleashing some 1.3 billion tons of TNT's worth of energy, said researcher Aaron Velasco, a seismologist at the University of Texas at El Paso. That is the equivalent of nearly 100,000 Hiroshima bombs, making it the second largest quake ever recorded with instruments. And the effects of earthquakes can be felt far and wide. The earthquake that just hit China, a magnitude 7.9, shook buildings in Shanghai at least 1,000 miles away from its epicenter in Sichuan.

New thinking

Until recently, scientists did not think major earthquakes set off smaller tremors at distant locations. Then, in 1992, they found that California’s magnitude-7.3 Landers earthquake set off small jolts as far away as Yellowstone National Park. While the 1992 findings suggested earthquakes could trigger smaller quakes nearby, how far major earthquakes could reach was a mystery. To investigate further, scientists analyzed 15 earthquakes of magnitude 7 or greater that occurred since 1990. These included the 2004 Indian Ocean earthquake, as well as the 1999 Izmit earthquake in Turkey that killed at least 15,000 and left a half-million homeless.

More Can big earthquakes trigger a domino effect? - LiveScience - MSNBC.com

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"There will be earthquakes in diverse places"...

Iceland shaken by magnitude 6.2 earthquake
May 29, `08 - A strong earthquake shook southern Iceland on Thursday, injuring at least 15 people as it rocked buildings in the capital, touched off landslides and forced evacuations in outlying towns, officials and local media said.

Government officials reported that 15 to 30 people were injured, none of the seriously, when the quake hit near Selfoss, 30 miles southeast of the capital of Reykjavik. They were taken to a local health center for treatment. The U.S. Geological Survey said the quake had a magnitude of 6.2 and hit at 3:46 p.m.

Sharp aftershocks were feared over the next few hours in the southwest of the country, and police traveled around the nearby town of Hveragerdi, 28 miles east of Reykjavik, with a bullhorn, advising residents to stay outdoors. An Associated Press Television News cameraman in Hveragerdi reported at least two aftershocks, and said residents were beginning to pitch tents outside because they were not allowed to return home.

"It was a horrific experience. Everything inside my house is ruined," Sveinn Ingvason, a 51-year-old construction worker, told Iceland's Channel 2 from the town. Adalheidur Gudmunsdottir, the 52-year-old director of nursing at a clinic in Selfoss, said many of her patients were frightened by the tremors. "Some of the patients asked to moved outside," she told Channel 2. "The initial idea was to evacuate the clinic ... (but) we decided to move beds from walls and close off the elevators."

More My Way News - Iceland shaken by magnitude 6.2 earthquake

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Wonder if this has anything to do with polar magnetic shift?...

Plan for quake 'warning system'
Thursday, 5 June 2008 - Nasa scientists have said they could be on the verge of a breakthrough in their efforts to forecast earthquakes.

Researchers say they have found a close link between electrical disturbances on the edge of our atmosphere and impending quakes on the ground below. Just such a signal was spotted in the days leading up to the recent devastating event in China. They have teamed up with experts in the UK to investigate a possible space-based early warning system. Many in the scientific community remain deeply sceptical about whether such signals are indeed indicators of an approaching earthquake.

But Minoru Freund, a physicist and director for advanced aerospace materials and devices at Nasa's Ames Research Center in California, told BBC News: "I do believe that we will be able to establish a clear correlation between certain earthquakes and certain pre-earthquake signals, in an unbiased way." "The evidence suggests we're now crossing the boundary in terms of technology readiness" - Stuart Eves, SSTL

He added: "I am cautiously optimistic that we have good scientific data, and we are designing a series of experiments to verify our data." Despite years of searching for earthquake precursors, there is currently no method to reliably predict the time of a future earthquake. Yet, most scientists agree that some form of early warning system could save tens of thousands of lives.

The ionosphere is distinguished from other layers of Earth's atmosphere because it is electrically charged through exposure to solar radiation. On a significant number of occasions, satellites have picked up disturbances in this part of the atmosphere 100-600km above areas that have later been hit by earthquakes. One of the most important of these is a fluctuation in the density of electrons and other electrically-charged particles in the ionosphere.

Early warning

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Quake early warning sign found...

Discovery may lead to quake early-warning system
Wed Jul 9, 2008 WASHINGTON - Scientists working at California's San Andreas Fault have detected subtle geological changes occurring hours before an earthquake that could enable them to develop an early-warning system aimed at saving lives.

Their instruments detected geological changes most likely caused by tiny fractures forming in the rock ahead of an impending earthquake due to stress in the Earth's crust, according to seismologist Paul Silver of the Carnegie Institution in Washington, one of the researchers. "It's the opening up of cracks before an earthquake," Silver said in a telephone interview.

The research, published on Wednesday in the journal Nature, was conducted using wells dug 0.6 miles (1 km) deep into the quake-prone fault at Parkfield, California. Their equipment generated and recorded seismic waves before, during and after two small quakes, allowing them to observe these small, predictive geological changes.

In the first case, the geological signals occurred 10 hours before a magnitude 3 quake in December 2005. The same sort of signals also occurred two hours before a magnitude 1 quake that happened five days later, the researchers said. "We are very encouraged by these observations, and we are planning for more experiments to confirm whether these changes are part of the general physical processes before an earthquake," seismologist Fenglin Niu of Rice University in Houston said in a telephone interview.

EVACUATIONS?