A tower for removing gas at the Marcellus Shale Formation in Pennsylvania.

When it was revealed in November that several small earthquakes in northwestern England had been caused by fracking, the controversial process of extracting shale gas from bedrock by cracking the rock with pressurized water, the gas company responsible stated that it was an extremely unlikely occurrence. True as that may be, residents of Youngstown, Ohio, can now testify that something similar has happened again. This time, it wasn’t the removal of shale gas that triggered the earthquakes, but apparently the subsequent cracking of sandstone in order to store the wastewater produced by fracking.

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Satellite radar data showed two wave fronts combining into a doubly tall tsunami off the coast of Japan on March 11.

The tsunami that spawned by the 9.0 earthquake off Japan this March was a disaster of massive proportions, reaching heights of over 130 feet in some areas and traveling up to six miles inland in others. Scientists at NASA and Ohio State University have now found another factor, beyond the sheer strength of the quake, that made the tsunami so ferocious: It started out as two separate walls of waves that combined to form one taller, more powerful “merging tsunami.”

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One cable holds the bridge up.

San Francisco has its share of massive earthquakes, but the Bay Bridge, one of the city’s main transit arteries, is not as quake-safe as you’d hope. That’s why, alongside it, the state is building a massive new replacement structure—the largest self-supporting suspension bridge ever built. Jim Giles at New Scientist went to visit the bridge and provides a primer on its engineering:

In a regular suspension bridge, the cables that support the roadway are hung between two or more towers, like a hammock between trees, and anchored at each end by a connection to land. The new bridge is more like a sling. A single cable loops under the roadway, over the tower and beneath the roadway on the other side of the tower. The enormous forces placed on the cable by the road cancel out, leaving a structure that is balanced but not directly supported by a land anchor…

As the [road] segment fell into place it revealed the full length of tower that stands behind it, an elegant structure made up of four concrete pillars. These drop into enormous steel foundations, parts of which were built in Texas and shipped to California via the Panama canal. The pillars are connected by “shear beams”—relatively weak steel components that are designed to break if the towers move. The two roadways, one each for east and westbound traffic, hang from the cables but are not attached directly to the tower. This arrangement means that the four pillars and two roadways will sway when a quake hits, but remain intact even through the strongest shaking that geologists expect the region to experience over the next 1500 years.

Read more at New Scientist.

Image courtesy of Bay Bridge Information Office.

The magnitude 5.8 quake that struck central Virginia on Tuesday was felt from Florida to Maine to Missouri. “This is probably the most widely felt quake in American history, even though it was less than a 6.0,” says Michael Blanpied, a USGS seismologist DISCOVER contacted after the event. The reason for this intensity is that the East Coast, like the controversial New Madrid Seismic Zone in the central U.S., is located amidst old faults and cold rocks in the middle of the North American tectonic plate, and seismic waves travel disturbingly far in such stiff, cold rock.

We would do well to take a hint from Tuesday’s expansive shake-up. It’s lucky that it struck in rural America. But a similar tremblor in the crowded cities of the central U.S. above the New Madrid zone is a matter of when, not if. And the region is woefully unprepared to mitigate the damage, as Amy Barth explores in a piece from an upcoming issue of DISCOVER:

The disastrous winter of 1811–12 is the stuff of legend in the Midwest. In the span of a few months, three major earthquakes rocked Missouri, Tennessee, and Arkansas, violently shaking 230,000 square miles stretching from St. Louis to Memphis. Witnesses claimed that the ground rolled in waves several feet high and the Mississippi River flowed backward. Some reports described buckling sidewalks in Charleston, South Carolina, and tremors that reached as far as Quebec. Had seismographs been available at the time, scientists believe those tremors would have registered magnitudes at least as great as the 7.0 quake that devastated Haiti in 2010 and possibly as high as 8.0. These would place them among the worst in U.S. history.

Read more…

What’s the News: The tsunami that deluged Japan in March was so strong that it broke off several large icebergs in Antarctica, 8,000 miles away, researchers report in a new paper [pdf]. Using satellite images, the researchers saw the tsunami causing new icebergs to split off—or calve—from an ice shelf, the first time such an event has been observed.

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The National Palace in Port-au-Prince
after the 2010 Haiti earthquake

What’s the News: To dampen structural vibrations from earthquakes, engineers often place a flexible layer of rubber bearings in between buildings and the soil. Now, scientists are learning that Mother Nature uses a similar technique. A research team has found that a buried layer of mangrove in the Caribbean island of Guadeloupe absorbs earthquake energy, shielding the above ground from soil liquefaction. This discovery could be exploited to help protect new buildings in the Caribbean islands.

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Destruction in L’Aquila, in the seismically active area of Abruzzi.

What’s the News: No one can predict earthquakes. But six seismologists and a government official are being tried for manslaughter in the deaths of more than 300 people in the 2009 tremblor in L’Aquila, Italy. The city’s public prosecutor says the scientists downplayed the possibility of a quake to an extent that townsfolk did not take precautions that could have saved their lives. A judge has just set the trial to begin on September 20.

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In this images of infrared radiation in the days before the March 11 earthquake, the red circle indicates the epicenter and the red lines are tectonic faults.

What’s the News: Scientists analyzing the March 11 earthquake in Japan will have the benefit of some of the most sensitive and comprehensive atmospheric data yet, thanks to satellites monitoring climate. And a team has now reported a strange effect—a sudden spike in the temperature in the atmosphere above the quake site—detected just before the event. If the spike was related to the quake, and other earthquakes do the same thing, it might help scientists predict such cataclysms in the future.

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A house decimated by the 2010 earthquake in Chile.

What’s the News: Enormous earthquakes are rare; there have been only seven quakes with a magnitude 8.8 or above since the start of the 20th century. Of those seven quakes, three of them have happened in the past seven years: off the coasts of Indonesia in 2004, Chile in 2010, and Japan last month. Some researchers think this earthquake cluster marks the start of a period of megaquakes, while others believe that the earthquake cluster is simply a statistical fluke, with these unusually massive quakes just happening to occur within a short amount of time, according to recent analyses (PDF) of Earth’s earthquake history presented at the Seismological Society of America’s annual meeting last week.

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At least 65 people died in an earthquake that struck New Zealand’s second-largest city, Christchurch, yesterday. As the city digs out from the rubble created by the magnitude 6.3 quake, some there are worried the death toll could climb into the hundreds. And as seismologists unravel the details, it’s becoming clear why this quake was so much deadlier than previous seismic events in New Zealand.

Photographs and video from Christchurch, a metropolitan area of nearly 400,000 residents, showed people running through the streets, landslides pouring rocks and debris into suburban streets and extensive damage to buildings. Witnesses told of watching the spire of the iconic Christchurch Cathedral come crashing down during an aftershock. One witness called it “the most frightening thing of my entire life,” and television footage showed a person clinging to a window in the cathedral’s steeple. [The New York Times]

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Chile’s earthquake woes seem to know no end. Geologists are now saying that Chile’s deadly 2010 quake may have actually increased the risk of another destructive one.

The 8.8-magnitude earthquake that struck last February relieved seismic stress in some areas–such as southern Santiago–but not in an area dubbed the “Darwin gap,” which lies on the coastal area near Concepcion, according to a study published in the journal Nature Geoscience.

To see if the 2010 quake might have helped release pent-up stress in the Darwin gap, scientists modeled how it might have affected the gap by analyzing tsunami readings gathered by gauges in the water and land observations taken by satellite, GPS and the human eye…. The investigators found the earthquake ruptured only part of the Darwin gap. An area of stored energy remains unbroken there, and the 2010 earthquake might have actually stressed it further…. [Said study coauthor Stefano Lorito]: “A new magnitude 7 to 8 earthquake might be expected in that region.” [OurAmazingPlanet]

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It’s beginning to look a lot like… self-inflicted doom.

This week Associated Press reporters tallied the toll of the year in natural disasters, and it added up to some depressing results. Around the world—in Haiti and Chile earthquakes, in Pakistani floods, in Russian heat waves—nature unleashed its fury in extreme fashion in 2010, the AP says, and humans made it worse through our own actions.

“It just seemed like it was back-to-back and it came in waves,” said Craig Fugate, who heads the U.S. Federal Emergency Management Agency. It handled a record number of disasters in 2010. “The term ’100-year event’ really lost its meaning this year.” [AP]

At least 250,000 people died in natural disasters this year, up from just 15,000 last year. But, the AP’s Seth Bornstein argues, this isn’t just natural variability.

For one thing, there are the avoidable problems of not doing enough to prepare for the inevitable appearance of disaster. The 2010 death toll is skewed so high this year because of the Haiti earthquake in January that killed most of the people in that quarter-million group. There’s nothing to be done about the shifts of tectonic plates, but the death toll skyrocketed because so many poor Haitians were living in such poorly built dwellings. The more powerful Chilean earthquake, by contrast, occurred in a place with better-built structures and killed fewer than a thousand. While in Pakistan, having so many homes in the flood zone exacerbated the damage when the monsoons came in July.

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As doctors try to contain the lethal outbreak of cholera in Haiti, geologists have more bad news for the island nation. The disastrous earthquake that struck in January did not release the stress on the main east-west fault that underlies Haiti, but in fact probably originated from a separate fault line, according to separate studies out in Nature Geoscience. That means Haiti is in danger of more major earthquakes.

Directly after the earthquake, some geologists said the most likely cause was Haiti’s Enriquillo-Plantain Garden fault, which has been building up pressure since the mid-1700′s. But not so, according to Eric Calais of the U.S. Geological Survey, who now says that an unmapped fault now named Léogâne was probably the source of the January disaster.

At first, scientists focused on the Enriquillo-Plantain Garden fault on Haiti’s southern peninsula — one of two main faults in the region. But the team said measurements of ground motion suggest the movement caused the surface to bulge, but not to rupture. Calais’ measurements led them to conclude a previously unknown fault must have caused the January quake. [ABC News]

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Originally scientists believed that one earthquake had set off the deadly tsunami that struck Samoa, American Samoa, and Tonga in September of 2009. But two studies to appear tomorrow in Nature argue that instead of one there were really two earthquakes that took place in rapid succession.

For some scientists, the studies clear up odd behavior that didn’t fit with the originally blamed “normal-fault” earthquake in the Pacific Northwest.

“We knew right off the bat that something was weird about this earthquake,” says geophysicist Eric Geist of the U.S. Geological Survey in Menlo Park, Calif. Geist wasn’t involved in the current studies but has puzzled over the anomalous signs produced by the quake. “This is a very complicated event, and these studies, for me, really helped explain a lot.” [Science News]

John Beaven, lead author of one of the studies, told Nature News the researchers expected the Tongan island to move about three inches to the west as a result of the quake, but GPS showed it had moved nearly a foot east. They also expected the sea bed to drop but instead it rose, a sign of a different kind of “megathrust” quake. A separate study led by Thorne Lay confirmed signs of this alternate type of earthquake from seismic readings.

Though both studies point to two different types of earthquakes, they disagree on which earthquake came first and caused the other. Ronald Burgmann, a geophysicist at the University of California, Berkeley, who was not involved in either study says, overall, they both make a good case:

“As in all good chicken-and-egg mysteries,” he says, “there is merit to both views.” [Nature News]

Related content:
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80beats: Major Earthquakes Can Weaken Faults Around the Globe
80beats: A Major Quake Could Release Plutonium from Los Alamos Lab

Image: Mick Finn, GNS Science

A magnitude 6.9 earthquake struck China’s southern Qinghai Province this week. The death toll now stand at more than 600, and rescuers pulled more than 1,000 people from the rubble alive. But, geologists say, this quake doesn’t seem linked to the massive one that shook the nearby province of Sichuan two years ago.

“It’s not the same fault, it’s a consequence of the same bit of global tectonics, which is the collision of India with Asia. That’s the only link I’d make,” said Dr David Rothery [BBC News]. The May 2008 Sichuan earthquake resulted from a thrust fault, which happens frequently in the region near the Himalayas where India and Asia collided long ago. But although this week’s quake happened not far from there, Rothery says it was a strike-slip event, which happens when there is sideways movement along a fault line. That’s the type of event that caused the January earthquake in Haiti.

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