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Gas Drilling


Many local residents have concerns about Gas Drilling in and around residential neighborhoods.   This does not mean they are anti-gas and oil, they just do not want it in their neighborhood.  In light of all that we know, and perhaps more important, what we do not know this is likeliest the safest for residential community such as Westchester.  It is better to error on the safe side when considering gas drilling in residential neighborhoods because there are simply too many unknowns and detailed research is still years away.  

The Army Corps of Engineers have declared a 3000 foot buffer from Gas Drilling "fracking” from its dams in Texas and many other states.   Unfortunately, the Corps of Engineers do not have complete control over land adjacent to dams they do not own.      Various regulatory agencies often do not work in harmony to always protect the rights of the general population that is concerned about such activities.
Fracking occurs thousands of feet deep and involve pressurizing shell around 8,000 pounds per square inch.   The entire process is designed to hydraulically fracture (frac)  the shale and force the trapped gas to the surface.   They are changing the geology with extremely high pressure in localized areas.    However these wells are often placed in a checker board fashion too.   
Wastewater disposal appears to be related to the magnitude-5.6 earthquake that struck rural central Oklahoma in 2011 leading to a few injuries and damage to more than a dozen homes. Damage from an earthquake of this magnitude would be much worse if it were to happen in a more densely populated area.  [i]

  [House damage in central Oklahoma from the magnitude 5.6 earthquake on Nov. 6, 2011. Research conducted by USGS geophysicist Elizabeth Cochran and her university-based colleagues suggests that this earthquake was induced by injection into deep disposal wells in the Wilzetta North field. Learn more about that research at: http://geology.gsapubs.org/content/early/2013/03/26/G34045.1.abstract. Photo Credit: Brian Sherrod, USGS.]
Dynamic triggering
Quakes with a magnitude of 2.0 or lower, which can hardly be felt, are routinely produced in fracking, says geologist William Ellsworth of the US 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 a commentary 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 5.0.
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."
"I have observed remote triggering in Oklahoma," says seismologist Austin Holland of the Oklahoma Geological Survey, who was not involved in the study. "This has occurred in areas where no injections are going on, but it is more likely to occur in injection areas."
Once these triggered quakes stop, the danger is not necessarily over. The swarm of quakes, says 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 6 November 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," says van der Elst. "[ii]
There is some evidence that increased seismic activity more than circumstance yet detailed studies are years away.    The gas companies are correct, there is no known connection but there are too many unknowns to be drilling in highly populated urban neighborhoods.   Most experts will say the same thing but most are now leaning toward the theory that there is a connection.      The U.S. Geological Survey says “the number of earthquakes has increased dramatically over the past few years within the central and eastern United States. Nearly 450 earthquakes magnitude 3.0 and larger occurred in the four years from 2010-2013, over 100 per year on average, compared with an average rate of 20 earthquakes per year observed from 1970-2000.

USGS scientists have found that at some locations the increase in seismicity coincides with the injection of wastewater in deep disposal wells. Much of this wastewater is a byproduct of oil and gas production and is routinely disposed of by injection into wells specifically designed for this purpose.”

Earth's crust is pervasively fractured at depth by faults. These faults can sustain high stresses without slipping because natural "tectonic" stress and the weight of the overlying rock pushes the opposing fault blocks together, increasing the frictional resistance to fault slip. The injected wastewater counteracts the frictional forces on faults and, in effect, "pries them apart", and thereby facilitating earthquake slip.

Are earthquakes induced by fluid-injection activities always located close to the point of injection?

“No. Given enough time, the injected fluids can migrate substantial horizontal and vertical distances from the injection location. Induced earthquakes commonly occur several kilometers below the injection point. In some cases, the induced earthquakes have been located as far as 10 km (6 mi.) from the injection well.” [iv]
This is particularly scary when you consider many wells are located like squares in a checkerboard about 5 miles apart.
Most people think we should develop all forms of energy to move toward more independence of foreign energy.    Electric and hybrids cars do not necessarily reduce pollution as the electricity is often produced by burning of fossil fuels.  However they do move the pollution away from urban areas where people live.    Likewise, Let’s work together to keep gas drilling out of highly populated urban areas until there is irrefutable proof Fracking  is safe in this setting.
[i] http://www.usgs.gov/blogs/features/usgs_top_story/man-made-earthquakes/
[ii] http://www.abc.net.au/science/articles/2013/07/12/3801578.htm
[iii] http://www.usgs.gov/faq/?q=categories/9833/3426
[iv] http://www.usgs.gov/faq/?q=categories/9833/3419
By Todd Hancock
Westchester Association, Grand Prairie Texas