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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The West Virginia coal mining accident yesterday killed at least 25, and hope is starting to fade for finding the four missing miners alive. It’s the deadliest mining accident in the United States in more than a quarter-century.

A methane explosion appears to be the cause. Normally when DISCOVER covers methane scares, it has to do with the potent greenhouse gas leaking from permafrost or the ocean. But for coal miners, methane represents a more clear and present danger: Underground mines can fill up with the flammable gas, and a stray spark can light it and cause an explosion. As a result, mines are required to have giant fans that blow methane out of the working area.

Methane not only appears to have caused the accident, it also held up the rescue effort. Operations had to be suspended because of a build-up of methane in the mine. It’s hoped that they can resume later today — but it will require drilling about 1,000 feet, through two coal seams, to get to where the men might have been able to find shelter [NPR].

Methane is ubiquitous in coal mines. The gas, like coal, is a molecule made of hydrogen and carbon, and it is produced from the same raw material as coal, ancient piles of biological material, by the same processes. Much of the natural gas sold in the United States is drawn from coal seams. In undisturbed coal deposits, the methane is kept loosely attached to the coal molecules by compression; when the area is opened up by miners, the pressure is reduced and the methane bubbles out [The New York Times].

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The wave of high-profile seismic activity so far in 2010 has been another reminder that we humans could use all the help we can get in predicting earthquakes. This week in the Journal of Zoology, biologist Rachel Grant suggests a new way: Watch the toads.

Taking cues from the animal kingdom is not itself a new idea (not by a long shot): Reports of animal earthquake prediction are legion and they date back to at least 373 BCE, when historians record that animals including rats, snakes and weasels flocked out of Helice just days before a quake devastated the Greek city. More recently there have been reports of catfish moving violently, bees leaving their hive in a panic, and fish, rodents, wolves and snakes exhibiting strange behaviour before earthquakes [Nature]. While these anecdotes grab the imagination, the scatter-shot nature of earthquakes previously prevented anyone from documenting such animal behavior before, during, and after a quake.

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When small earthquakes rumbled beneath northern Texas in 2008 and again in 2009, scientists were puzzled. While they expect to see seismic activity in active zones like Haiti, Chile, and Turkey, where disasters have already struck this year, the area around Fort Worth, Texas sees only rare and tiny seismic activity. Now, some Texas seismologists are arguing that techniques used in conjunction with natural gas exploration provide a plausible explanation for what’s going on.

North Texas sits atop the Barnett Shale, one of the several giant layers of shale in the United States believed to hold a truly massive amount of natural gas. The U.S. Geological Survey estimates that 200 trillion cubic feet of natural gas may reside in shales nationwide [USA Today]. The reason these giant deposits have remained largely untapped, however, is that shale isn’t particularly porous, and so extracting it requires drillers to fracture the rock in multiple places.

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The magnitude 8.8 earthquake that rocked Chile on February 27th didn’t just move the Earth’s axis, thereby shortening the day by 1.26 microseconds, but it also caused entire cities to shift their geographical location.

Studying precise GPS images of the area struck by the quake, a team led by earth scientist Mike Bevis discovered that the Chilean city of Concepción had moved 10 feet to the west. The epicenter of the quake was 71 miles northeast of Concepción, which is Chile’s second largest city.

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Less than two months after the earthquake that shook Haiti, and only hours after a quake causing small tsunamis occurred near Japan, the largest of 2010′s seeming barrage of big seismic events hit Chile. The 8.8 earthquake is the fifth largest since 1900. “We call them great earthquakes. Everybody else calls them horrible,” said USGS geophysicist Ken Hudnut. “There’s only a few in this league” [AP].

According to seismologists, the confluence of earthquakes these last couple months are probably coincidental; they’re all separated by too great a distance to be directly related. However, some say the latest quake is related to the 1960 quake in Chile that remains the largest ever recorded, a 9.5 on the Richter scale. Both earthquakes took place along a fault zone where the Nazca tectonic plate, the section of the earth’s crust that lies under the Eastern Pacific Ocean south of the Equator, is sliding beneath another section, the South American plate [The New York Times]. That massive event increased stress on other parts of the fault line, which continued to increase as the two plates converged at three and a half inches per year.

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NASA is sending a radar-equipped jet to conduct flights over Haiti and the Dominican Republic to capture 3-D images that could help predict future earthquakes. An estimated 170,000 people were killed in the 7.0 earthquake that battered Haiti on January 12. Unfortunately, experts predict more quakes as the country is situated in a seismically volatile zone.

A Gulfstream III jet is now on its way to map Haiti and the Dominican Republic, the two nations that share the island of Hispaniola. The Uninhabited Aerial Vehicle Synthetic Aperture Radar, or UAVSAR, was originally on its way to Central America to study volcanoes, forests, and Mayan ruins, but on its way south it will now also study Hispaniola’s fault lines.

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In the aftermath of Haiti’s devastating earthquake, nervous citizens can be forgiven for wondering where the next Big One will hit. Major quakes strike with alarming regularity: Earthquakes of magnitude 7 or greater occur approximately 18 times a year worldwide. They usually originate near faults where tectonic plates —tremendous fragments of the earth’s crust—collide or push above or below each other.

Geologists suspect that Haiti’s destructive quake resulted from 250 years of seismic stress that has been building up between the North American and Caribbean tectonic plates. In fact, a group of U.S. geologists presented a study in the Dominican Republic (which shares the island of Hispaniola with Haiti) in 2008 saying that the region was at risk of an earthquake potentially even bigger than last week’s magnitude 7.0 quake. Part of their presentation is particularly chilling in light of what would happen less than two years later: “This means that the level of built-up stress and energy in the earth could one day be released resulting in an earthquake measuring 7.2 or more on the Richter Scale. This would be an event of catastrophic proportions in a city [Port-au-Prince] with loose building codes, and an abundance of shanty-towns built in ravines and other undesirable locations.”

Earthquakes are still impossible to predict with precision; in the words of one of the geologists who predicted the Haiti quake, “It could have been the next day, it could have been 10 years, it could have been 100… This is not an exact science.” But researchers have identified a handful of seismic zones around the globe that are storing up especial amounts of stress and are particularly hazardous. Browse through the gallery for a world tour of the planet’s most seismically vulnerable regions.

By Aline Reynolds

Image: USGS

Satellite photos that have just been released reveal the scope of the physical destruction wrought by the 7.0 earthquake that struck the Haitian capital of Port-au-Prince on Tuesday. The human toll of  is still unknown–but with much of the city reduced to rubble, experts say tens of thousands of people may be dead.

This image shows roads covered with debris from collapsed structures, and the white-colored National Palace with damage visible along the roof line. The image was taken by the GeoEye-1 satellite from 423 miles up in space on Wednesday morning.

Image: GeoEye

As Haiti reels from yesterday’s massive earthquake and its continued aftershocks, and nations rush to put rescue efforts together, scientists analyzing the seismic event say this disaster may have been a long time coming.

The earthquake in Haiti had a preliminary magnitude of 7.0 and it appeared to have occurred along a strike-slip fault, where one side of a vertical fault slips horizontally past the other, scientists say [AP]. This fault, called the Enriquillo-Plantain Garden fault, may have been slowly building up pressure since the major 1760 earthquake that struck Haiti.

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Twitter: Bane of employers … but friend of science?

At a scientific meet-up in California this week, researchers with the U.S. Geological Survey proposed that the 140-character micro-blogging site could help to speed up responses to earthquakes. “Why would such a system work?” asked Paul Earle, a geologist at the USGS, at the American Geophysical Union fall meeting Monday. “Because people like to tweet after an earthquake” [Wired.com].

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Dreams that major geothermal energy plants could power our future took a major hit last week, as worries over earthquakes and technical failures killed two ambitious projects in consecutive days. The two projects both hoped to harvest the heat of deeply buried bedrock by drilling down, fracturing the rock, and then circulating water through the fissures to produce steam that could drive turbines.

First, on Thursday, the $60 million plan to tap geothermal energy beneath Basel, Switzerland, died for good after a Swiss government study said it would cause millions of dollars in damage through earthquakes each year. The project, led by Markus O. Häring, a former oilman, was suspended in late 2006 after it generated earthquakes that did no bodily harm but caused about $9 million in mostly minor damage to homes and other structures. Mr. Häring is to go to trial next week on criminal charges stemming from the project [The New York Times].

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Federal experts believe that a major earthquake could trigger fires at Los Alamos National Laboratory, releasing radioactive materials and endangering lives. The rupture of a seismic fault that runs underneath the lab would shake the ground more than scientists previously thought, according to a new report (PDF). A natural disaster here would be bad news, since the lab, just west of Santa Fe, is the main plutonium factory in the United States, believed to hold thousands of pounds of plutonium for use in nuclear weapons (the actual amount is classified).

Researchers study plutonium inside glove boxes—a Hollywood movie staple, consisting of a sealed enclosure with gloves so that someone outside the box can work on dangerous materials inside. A major earthquake would shake the ground enough to topple the glove boxes, says the new study. Some glove boxes are enormous and even contain furnaces to cast and mold plutonium. If one of these were to crash, the resulting fire would be uncontrollable and would create a vaporized plutonium cloud that could drift outside of the lab, says the safety report. In a worst-case scenario, a fire could release so much airborne plutonium that a person on the boundary of the lab would get a dose of radiation—potentially many thousands of times greater than a chest X-ray—that could be fatal in weeks, according to individuals knowledgeable about the study [Los Angeles Times].

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Here’s a timely piece of research that may inspire some trepidation, as it comes hard on the heels of Tuesday’s tsunami-triggering earthquake in the South Pacific and today’s destructive earthquake in Indonesia. Researchers have found evidence that major quakes can weaken faults on the other side of the world, increasing the chance of further tremors.

The researchers analyzed 20 years of data at Parkfield, which sits on the mighty San Andreas Fault halfway between Los Angeles and San Francisco. It’s the most studied earthquake zone in the world, rigged with sensitive instruments to detect minute changes in the Earth’s crust [AP]. In 2004, the seismic records showed a change beginning shortly after the 9.3 magnitude earthquake in Sumatra that caused a deadly tsunami.

There was an increase in the number of small “repeating earthquakes” that regularly shudder through the ground around the San Andreas fault. Study coauthor Taka’aki Taira says that “after Sumatra, the frequency changed – it increased – but the magnitude decreased. That is a signal of the fault weakening; you only have to push a little bit and the fault fails” [BBC News].

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The tsunami that struck the South Pacific islands of Somoa, American Somoa, and Tongo yesterday has resulted in at least 108 deaths, according to early reports.

Experts monitoring the underwater earthquake that triggered the tsunami have issued various reports of its magnitude, ranging from 7.8 to 8.3. The powerful quake struck early on Tuesday morning, local time, as island residents were getting ready for work and school. About ten minutes after the shock, ten-foot-high waves hit American Somoa’s shore. “American Samoa is a small island, and most of the residents are around the coastline,” [said Filipo Ilaoa, deputy director of the American Samoan office in Honolulu]. “There was no warning or anything at all. By the time the alert was out of the Pacific Tsunami Warning Center, it had already hit” [The New York Times].

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