Nicholas van der Elst, the lead author on one of three studies published on Thursday in the journal Science said:
“These fluids are driving faults to their tipping point.”
Pumping water underground could trigger major earthquake, say scientists, New studies suggest injecting water for geothermal power or fracking can lead to larger earthquakes than previously thought by Natalie Starkey, July 11, 2013, The Guardian
Pumping water underground at geothermal power plants can lead to dangerous earthquakes even in regions not prone to tremors, according to scientists. They say that quake risk should be factored into decisions about where to site geothermal plants and other drilling rigs where water is pumped underground – for example in shale gas fracking.
Prof Emily Brodsky, who led a study of earthquakes at a geothermal power plant in California, said: “For scientists to make themselves useful in this field we need to be able to tell operators how many gallons of water they can pump into the ground in a particular location and how many earthquakes that will produce.”
It is already known that pumping large quantities of water underground can induce minor earthquakes near to geothermal power generation and fracking sites. However, the new evidence reveals the potential for much larger earthquakes, of magnitude 4 or 5, related to the weakening of pre-existing undergrounds faults through increased fluid pressure.
The water injection appears to prime cracks in the rock, making them vulnerable to triggering by tremors from earthquakes thousands of miles away. Nicholas van der Elst, the lead author on one of three studies published on Thursday in the journal Science said: “These fluids are driving faults to their tipping point.”
Prof Brodsky said they found a clear correlation between the amount of water extracted and injected into the ground, and the number of earthquakes.
The analysis of the Californian site showed that for a net injection of 500m gallons of water into the ground per month, there is an earthquake on average every 11 days.
“The problem is we can only predict how many earthquakes will occur but not their size and so with this knowledge then it has to be decided what is an acceptable size and frequency of earthquakes for a particular area,” said Brodsky.
Because of the increase in the exploitation of geothermal power for renewable energy, and hydraulic fracturing or “fracking” to release natural gas, it is important to understand the chances of a large earthquake occurring at these sites, particularly if they are in densely populated regions.
Another key feature of the research shows that sites experiencing sustained pumping of water into the ground for a period of decades or more are more susceptible to large tremors triggered by earthquakes occurring in other parts of the world.
Large earthquakes in Chile in 2010, Japan in 2011 and Sumatra in 2012 all set off mid-size tremors in the central United States near to sites of water injection, with the largest induced earthquake of magnitude 5.7 destroying 14 homes and injuring two people. Van der Elst said: “The remote triggering by big earthquakes is an indication the area is critically stressed.”
Heather Savage, a co-author on the same study said: “It is already accepted that when we have very large earthquakes seismic waves travel all over the globe, but even though the waves are small when they reach the other side of the world, they still shake faults. This can trigger seismicity in seismically active areas such as volcanoes where there is already a high fluid pressure. But this is the first time the same has been recognised for areas with anthropogenically induced high fluid pressure.”
Scientists map the exact location of faults that occur naturally over most of the Earth’s crust. However, there are many underground faults that do not intersect the Earth’s surface, some of which could be very large. The fear is that one of these previously inactive faults could be triggered. Van der Elst added: “It is an important subject for the future that we understand about the disposal of fluids as they arise from many processes.” [Emphasis added]
Fracking linked to earthquakes, study finds by Agence France-Presse, July 11, 2013, Raw Story
Large earthquakes around the world have been found to trigger tremors at US sites where wastewater from gas drilling operations is injected into the ground, a US study said Thursday. For instance, the massive 9.0 magnitude earthquake in Japan in 2011 set off a swarm of earthquakes in the western Texas town of Snyder near the Cogdell oil field, culminating in a 4.5 magnitude quake there about six months later, said the research in the journal Science. Similarly, small to mid-sized quakes were observed near active injection wells in Prague, Oklahoma following an 8.8 magnitude quake in Chile in 2010. Uncommon seismic activity stirred that region 16 hours after the Chile quake with a 4.1 magnitude tremor, and it continued until a 5.7 magnitude quake in November 2011, said researchers at Columbia University’s Lamont-Doherty Earth Observatory. The 2010 Chile quake also led to heightened seismic activity in Trinidad, Colorado, including a 5.3 magnitude quake in August 2011, in an area where methane is extracted from the coal bed and wastewater is reinjected into the Earth.
“We weren’t really confident until we found the same pattern of little bursts of seismicity following the passage of seismic waves from several of these big earthquakes,” lead author Nicholas van der Elst of Columbia University told AFP. “Any individual case could be a coincidence but once you start observing it systematically, then you can have more confidence that you are really looking at a physical relationship.” The study helps explain a surge in earthquakes in the central United States, which in recent years has seen a more than six-fold increase in earthquakes over 20th century levels.
An accompanying study in Science said there were 300 3.0-magnitude or higher earthquakes in the central United States from 2010 to 2012, after an average of 21 such quakes per year from 1967 to 2000. The change coincides with a growing natural gas boom that is based on using large amounts of fluids to crack open rocks for natural gas, known as hydro-fracturing or fracking.
… The US Department of the Interior last year also acknowledged an uptick in seismic activity — predominantly in Texas, Colorado, Arkansas, Oklahoma and Ohio — where disposal of wastewater through injection wells has “increased significantly,” it said. One of the earliest known cases of wastewater inducing earthquakes dates back to the Rocky Mountain Arsenal Well near Denver, Colorado, where large amounts of wastewater were injected from 1962 to 1966, leading to a series of earthquakes below magnitude 5.0, the DOI said. … But the new research raises questions about how to manage the risks of causing quakes associated with oil and gas extraction and disposal of wastewater in underground wells.
“These passing seismic waves are like a stress test,” said co-author Heather Savage, a physicist at Lamont-Doherty. “If the number of small earthquakes increases, it could indicate that faults are becoming critically stressed and might soon host a larger earthquake.” The largest so far has been the 5.7 magnitude quake on November 6, 2011 in Prague, Oklahoma, triggered by the Chilean quake a year earlier. The US quakes have been felt by many people but have caused minimal damage and no deaths, though researchers point out that elsewhere in the world, similarly strong quakes have resulted in massive damage and loss of life. Scientists have no way of predicting when a particular field has reached a dangerous point, which van der Elst and colleagues described as a “key problem in developing operational strategies” to lessen the earthquake risk posed by human activities.
In an accompanying article in Science, William Ellsworth of the US Geological Survey framed the problem another way. “Ignorance of the things that we understand we should know but do not leaves us vulnerable to unintended consequences of our actions,” Ellsworth said. [Emphasis added]
Study raises new concern about earthquakes and fracking fluids by Sharon Begley, additional reporting by Edward McAllister, July 11, 2013, Reuters
Powerful earthquakes thousands of miles away can trigger swarms of minor quakes near wastewater-injection wells like those used in oil and gas recovery, scientists reported on Thursday, sometimes followed months later by quakes big enough to destroy buildings. The discovery, published in the journal Science by one of the world’s leading seismology labs, threatens to make hydraulic fracturing, or “fracking,” which involves injecting fluid deep underground, even more controversial. It comes as the U.S. Environmental Protection Agency conducts a study of the effects of fracking, particularly the disposal of wastewater, which could form the basis of new regulations on oil and gas drilling.
Geologists have known for 50 years that injecting fluid underground can increase pressure on seismic faults and make them more likely to slip. The result is an “induced” quake. … Now seismologists at Columbia University say they have identified three quakes – in Oklahoma, Colorado and Texas – that were triggered at injection-well sites by major earthquakes a long distance away. “The fluids (in wastewater injection wells) are driving the faults to their tipping point,” said Nicholas van der Elst of Columbia’s Lamont-Doherty Earth Observatory in Palisades, New York, who led the study. It was funded by the National Science Foundation and the U.S. Geological Survey.
Fracking opponents’ main concern is that it will release toxic chemicals into water supplies, said John Armstrong, a spokesman for New Yorkers Against Fracking, an advocacy group. But “when you tell people the process is linked to earthquakes, the reaction is, ‘what? They’re doing something that can cause earthquakes?’ This really should be a stark warning,” he said. … Quakes with a magnitude of 2 or lower, which can hardly be felt, are routinely produced in fracking, said geologist William Ellsworth of the U.S. Geological Survey, an expert on human-induced earthquakes who was not involved in the study. The largest fracking-induced earthquake “was magnitude 3.6, which is too small to pose a serious risk,” he wrote in Science.
But van der Elst and colleagues found evidence that injection wells can set the stage for more dangerous quakes. Because pressure from wastewater wells stresses nearby faults, if seismic waves speeding across Earth’s surface hit the fault it can rupture and, months later, produce an earthquake stronger than magnitude 5. What seems to happen is that wastewater injection leaves local faults “critically loaded,” or on the verge of rupture. Even weak seismic waves from faraway quakes are therefore enough to set off a swarm of small quakes in a process called “dynamic triggering.” … Once these triggered quakes stop, the danger is not necessarily over. The swarm of quakes, said Heather Savage of Lamont-Doherty and a co-author of the study, “could indicate that faults are becoming critically stressed and might soon host a larger earthquake.”
For instance, seismic waves from an 8.8 quake in Maule, Chile, in February 2010 rippled across the planet and triggered a 4.1 quake in Prague, Oklahoma – site of the Wilzetta oil field – some 16 hours later. That was followed by months of smaller tremors in Oklahoma, and then the largest quake yet associated with wastewater injection, a 5.7 temblor in Prague on November 6, 2011. That quake destroyed 14 homes, buckled a highway and injured two people. The Prague quake is “not only one of the largest earthquakes to be associated with wastewater disposal, but also one of the largest linked to a remote triggering event,” said van der Elst.
The Chile quake also caused a swarm of small temblors in Trinidad, Colorado, near wells where wastewater used to extract methane from coal beds had been injected. On August 22, 2011, a magnitude 5.3 quake hit Trinidad, damaging dozens of buildings.
The 9.1 earthquake in Japan in March 2011, which caused a devastating tsunami, triggered a swarm of small quakes in Snyder, Texas – site of the Cogdell oil field. That autumn, Snyder experienced a 4.5 quake. … Guy, Arkansas; Jones, Oklahoma; and Youngstown, Ohio, have all experienced moderate induced quakes due to fluid injection from oil or gas drilling. But none has had a quake triggered by a distant temblor. Long-distance triggering is most likely where wastewater wells have been operating for decades and where there is little history of earthquake activity, the researchers write.
“The important thing now is to establish how common this is,” said Oklahoma’s Holland, referring to remotely triggered quakes. “We don’t have a good answer to that question yet.”
Before the advent of injection wells, triggered earthquakes were a purely natural phenomenon. A 7.3 quake in California’s Mojave Desert in 1992 set off a series of tiny quakes north of Yellowstone National Park in Wyoming, for instance. Now, according to the Science paper, triggered quakes can occur where human activity has weakened faults. Current federal and state regulations for wastewater disposal wells focus on protecting drinking water sources from contamination, not on earthquake hazards. [Emphasis added]
Japanese earthquake caused tremors around U.S. oilfield, study suggests by Alicia Chang, July 12, 2013, The Associated Press in Calgary Herald
“The seismic waves act as the straw that breaks the camel’s back, pushing the faults that last little bit toward an earthquake,” lead researcher Nicholas van der Elst said in an email.
There has been heightened scrutiny in recent years of quakes near industrial areas as drilling is ramped up to satisfy the country’s energy hunger. Research has shown that wastewater disposal — the process of pumping fluids deep into the ground at high pressures — can weaken nearby fault lines and even produce quakes big enough to be felt. … If the observations bear out, it could help oil and gas operators know “where it’s safe to inject and where it’s not,” said Julie Shemeta, a geophysicist and president of Colorado-based MEQ Geo Inc., a consulting company.
Despite a history of man-made quakes near wastewater injection sites, only a small number of the country’s 30,000 disposal wells are a problem, said U.S. Geological Survey seismologist William Ellsworth, who published an article in the journal reviewing the state of research. Ellsworth said fracking does not pose a high risk for triggering quakes strong enough to feel. The largest man-made quake linked to fracking was a magnitude-3.6 in British Columbia in 2009. [Emphasis added]