Seismologist says quakes likely tied to drilling

05/02/2014 11:03 AM

05/02/2014 11:05 AM

The swarm of earthquakes rattled homes for months in North Central Texas, with reports of broken water pipes and cracked walls, and locals blamed the fracking boom that’s led to skyrocketing oil and gas production nationwide.

Darlia Hobbs, who lives on Eagle Mountain Lake, said more than 30 quakes hit from November to January.

“We have had way too many earthquakes out here because of the fracking and disposal wells,” she said in an interview.

While the dispute over the cause continues, leading geophysicists now say Hobbs and other residents might be right to point the finger at oil and gas activities.

“It is certainly possible, and in large part that is based on what else we’ve seen in the Fort Worth basin in terms of the rise of earthquakes since 2008,” William Ellsworth, a U.S. Geological Survey seismologist, said in an interview Thursday.

Ellsworth said the Dallas-Fort Worth region previously had just a single known earthquake, in 1950.

Since 2008, he said, there have been more than 70 big enough to feel. Those include earthquakes at Dallas/Fort Worth Airport that scientists linked to a nearby injection well.

Ellsworth briefed his colleagues on his findings Thursday at the Seismological Society of America’s annual meeting in Anchorage, Alaska.

Researchers are also investigating links between quakes in Kansas, Oklahoma, Ohio and elsewhere to oil and gas activities. USGS seismologist Art McGarr said it’s clear that deep disposal of drilling waste was responsible for at least some of the earthquakes.

“It is only a tiny fraction of the disposal wells that cause earthquakes large enough to be felt and occasionally cause damage,” McGarr said. “But there are so many wells distributed throughout much of the U.S. they still add significantly to the total seismic hazard.”

While causes are under debate, it’s well-established that earthquakes have spiked along with America’s fracking boom. The USGS reports that an average of more than 100 earthquakes a year with a magnitude of 3.0 or more hit the central and eastern U.S. in the past four years.

That compares with an average of only 20 observed quakes a year from 1970 to 2000.

But the USGS considers it very rare for fracking itself to cause quakes. Far more often, the issue is quakes caused by the disposal of the wastewater into wells.

The Texas Railroad Commission is skeptical of the link between earthquakes and drilling.

“The commission bases its regulation on science and facts, and at this time staff have no information or science that warrants limits to drilling or hydraulic fracturing in Texas,” spokeswoman Gaye McElwain said in an email.

Ellsworth said that near Fort Worth, two disposal wells were close enough to the earthquakes to be responsible. He said more research is needed to determine whether they were the cause or whether the natural gas production itself in the Barnett Shale was responsible.

In their presentation Thursday, Ellsworth and his colleagues, including seismologists from Southern Methodist University, ruled out the idea that the falling level of a nearby lake might be contributing.

But he said they can’t entirely reject the possibility of other natural causes — even though earthquakes were virtually unheard-of in the region before 2008, a time frame that matches the start of the fracking boom.

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