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Originally posted by loam
reply to post by loam
Can one of you guys assess this link? Would it have any relationship to the reason for your missing data?
The number and strength of earthquakes in central Arkansas have noticeably dropped since the shutdown of two injection wells in the area, although a state researcher says it’s too early to draw any conclusions.
The Center for Earthquake Research and Information recorded around 100 earthquakes in the seven days preceding the shutdown earlier this month, including the largest quake to hit the state in 35 years — a magnitude 4.7 on Feb. 27. A dozen of the quakes had magnitudes greater than 3.0. In the days since the shutdown, there have been around 60 recorded quakes, with only one higher than a magnitude 3.0. The majority were between magnitudes 1.2 and 2.8.
The two injection wells are used to dispose of wastewater from natural-gas production. One is owned by Chesapeake Energy, and the other by Clarita Operating. They agreed March 4 to temporarily cease injection operations at the request of the Arkansas Oil and Gas Commission.
The commission said preliminary studies showed evidence potentially linking injection activities with nearly 1,000 quakes in the region over the past six months.
Experts are looking for a reason behind Tuesday afternoon’s unlikely 5.8 magnitude earthquake that shook people up and down the East Coast, and some are saying that a recent rise in fracking could be the culprit.
Hydraulic fracturing, or “fracking,” is the man-made splintering of underground rocks to expedite the exploiting of natural resources. It’s become a widespread phenomenon since its introduction in 2004, and though the practice can help increase supplies of oil and gas without reaching out internationally for imports, the result it can have on the geological make-up of the Earth can be ravaging. Now some experts say the rise in fracking could be to blame for yesterday’s quake.
The odds of a quake exceeding a magnitude of 5.5 occurring in central Virginia are so slim that Dominion Power determined only around six quakes of that size would occur in the area over the next 10,000 years.
Explicitly, the United States Geological Survey has published a finding confirming that processes like fracking can be to blame for “natural” disasters. "Earthquakes induced by human activity have been documented in a few locations in the United States, Japan and Canada,” writes the USGS. “The cause was injection of fluids into deep wells for waste disposal and secondary recovery of oil and the use of reservoirs for water supplies."
Out West, geologists have blamed fracking on earthquakes that unexpectedly shook up the state of Arkansas, which recently saw over 20 small tremors in a single day. Freak earthquakes have also occurred in regions of Texas, New York and Oklahoma that should not be likely sites of epicenters, though those locales have all seen a rise in fracking in recent years.
Monday’s 5.3-magnitude earthquake southwest of Trinidad in southern Colorado is being called rare but “consistent with the region and historic activity in the area,” and so far no official connection is being made to gas drilling — or hydraulic fracturing — of relatively shallow coal-bed methane gas reserves in the area.
But such a connection to so-called “fracking” and the disposal of fracking fluid in the local gas fields has been investigated by the U.S. Geological Survey (USGS) in the past. A September 2001 swarm of earthquakes prompted a USGS investigation.
“In recent years, a large volume of excess water that is produced in conjunction with coal-bed methane gas production has been returned to the subsurface in fluid disposal wells in the area of the earthquake swarm,” the USGS report reads. “Because of the proximity of these disposal wells to the earthquakes, local residents and officials are concerned that the fluid disposal might have triggered the earthquakes.
“We have evaluated the characteristics of the seismicity using criteria proposed by Davis and Frohlich (1993) as diagnostic of seismicity induced by fluid injection. We conclude that the characteristics of the seismicity and the fluid disposal process do not constitute strong evidence that the seismicity is induced by the fluid disposal, though they do not rule out this possibility.”
In March, Arkansas oil and gas regulators instituted an emergency moratorium on fracking to determine whether injection wells might be behind a swarm of earthquakes in that state. Fracking involves injecting large quantities of water, sand and often undisclosed chemicals into natural gas wells to fracture rock formations and free up more gas. The water is then stored in holding ponds on the surface for re-use in future “frack jobs” and is later re-injected into disposal wells.
In June, the U.S. Environmental Protection Agency (EPA) announced seven sites for an ongoing retrospective study of the impacts of fracking on drinking water supplies. One of the sites is in the Raton Basin in Las Animas County, Colo., scene of Monday’s earthquake.