By Kristin Van Veen-Hincke
On Nov. 5, 2011, the talk of the Sooner State wasn’t focused on the respective football games played that day in Norman and Stillwater. Nor was it the severe and differing weather patterns hitting the state. No, the hot topic of that day occurred approximately 44 miles east of the state capital when a 5.6-magnitude earthquake struck near Prague. This tremor, believed to be the largest in the state since a 5.5-magnitude quake hit the southwest part of the state on April 9, 1952, caused injury to two people, destroyed 14 homes, and was felt from Texas to Kansas.
The quake wasn’t a surprise to Oklahoma State Representative Danny Morgan, whose family owns Morgan Well Service in Prague.
“In June, our local chamber of commerce sponsored a meeting with the Oklahoma State Geological Survey,” he said. “They talked about an uplift fault in our area. They were monitoring small movements that were registering on their equipment. They said it was like a volcano – at some point in time it was going to happen. Sure enough, we got hammered!”
Morgan wasn’t at home in Prague when the quake occurred, but he felt the tremor as he was leaving the Oklahoma State football game in Stillwater.
“It is a very unique experience,” he commented. “I had never been through one before. In fact, we had a tornado on the ground in southwest Oklahoma, flooding in the northern part of the state, and then the earthquake all in the same day. The only thing we were missing was the locusts.”
In the weeks following the November 5 quake, the area around Prague experienced almost a dozen aftershocks. In response to this activity, the city hosted a community meeting to answer residents’ questions. The nearly 900 attendees heard from representatives of the Oklahoma Geological Survey as well as the state’s insurance commissioner.
“There was a group that wanted to find fault with the oil and gas industry,” Morgan acknowledged, “wanting to know if this was the result of disposal wells pumping large amounts of water into the ground. The folks from the Geological Survey said the earthquake was several miles deeper than any fracturing or injection wells. I finally stood up and said this meeting is not to find fault. We think it was nature taking its course. We believe it was the subsurface pushing up. In Oklahoma, we don’t ask who caused a tornado. In California, they don’t ask who caused an earthquake. But earthquakes are so rare here that some people want to find fault because we had one.”
Growing concern surrounding the oil and gas extraction method of hydraulic fracturing and the disposal of the produced water that results from production activities has led doubters from Oklahoma to Ohio to West Virginia to England to question the industry’s methods.
When the November 5 quake occurred, Oklahoma seismologist Austin Holland had just completed a study of earthquakes for the Oklahoma Geologic Survey on a small cluster of tremors that occurred in January 2011 near Elmore City. He had determined that those quakes were naturally occurring.
“At present, we can link very few earthquakes to oil and gas industry activities,” he stated. “We are examining this as a possibility, but it is not a simple thing to determine because the energy to cause the earthquakes is already in the subsurface on the faults, and we do not know how oil and gas activity has changed the stresses deep within the earth. We are working to get a better understanding of what earthquakes may be linked to oil and gas.”
This is not the first time oil and gas activities have been linked to earthquakes in Oklahoma. In 1978, 70 small quakes occurred in just over six hours, leading residents and industry officials to question the extraction methods used at the time. Just a decade later, 90 small tremors were linked to fracturing. Both of these studies lacked conclusive data, and a concrete connection to oil and gas methods was never realized. It should be noted that 1.2 million wells have been fracked over the past 60 years in the U.S., with 100,000 of those occurring in Oklahoma.
In April, a group of scientists led by geophysicist William Ellsworth, a former president of the Seismological Society of America now working at the Geological Survey’s Earthquake Science Center in Menlo Park, California, presented a paper at the annual meeting of the Society acknowledging the increased frequency of earthquakes in the middle part of the country beginning in 2001. In 2009, 50 earthquakes greater than magnitude 5.0 occurred between Alabama and Montana, while 87 occurred in that same area in 2010. The 134 quakes recorded in the same area last year represented a six-fold increase over 20th century levels. The research attributed this rise in tremors to injection wells. The paper also noted that in Oklahoma, the rate of earthquakes greater than a 3.0 on the Richter scale “abruptly increased” from an average of 1.2 per year for the previous 50 years to more than 25 in 2009 alone. However, Holland’s research found that most of the state’s seismic activity did not appear to be tied to injection wells.
Conversely, University of Memphis seismologist Stephen Horton presented a paper at the Seismological Society of America meeting that did conclude that the November earthquake was “possibly triggered” by waste injection wells located near the epicenter. There are 181 injection wells in Lincoln County. Horton warned that Oklahoma officials are risking another large earthquake if oil and gas companies are allowed to inject waste near the same fault.
It has been a long held belief among scientists that injecting water underground, no matter the source, can lubricate faults and cause earthquakes. However, there are approximately 40,000 oil and gas disposal wells across the country, and only a handful have been linked to any seismic activity.
In the last year, earthquakes in Arkansas and Ohio have forced the shutdown of injection wells, as well as the development of new regulations guiding their use. Horton’s research in Arkansas caused state officials to ban injection wells in part of the state. While there is no federal law against causing earthquakes, a class-action lawsuit against oil and gas companies accusing negligence in response to the increase in earthquakes in Arkansas is now working its way through the federal court system.
Oklahoma state geologist G. Randy Keller and Colorado state geologist Vince Matthews have criticized the research conducted by Ellsworth and Horton as premature. However, University of Oklahoma seismologist Katie Keranen believes there is a “compelling link between the zone of injection and the seismicity.” She began placing seismic instruments in the ground after a 4.7-magnitude earthquake shook the Prague area just days before the November 5 event. However, she cautions that the state has naturally occurring seismic activity that “complicates things.”
There was one issue everyone seemed to agree on at the Society’s annual meeting: fracking does not refer to the entire process of shale drilling. While these experts may disagree on the part that injection wells play in the recent increase in seismic activity, they all understand and strive to clarify that there is no connection between fracking and earthquakes. Environmentalists and the media are hard pressed to accept that distinction. In a recent interview on CNBC, the host seemed frustrated when Ellsworth continued to emphasize that the link his research shows is between injection wells and earthquakes, not fracking and earthquakes.
The federal government even weighed in on the subject in June when the Senate Energy and Natural Resources Committee held a hearing on a report issued by the National Research Council. The report, sponsored by the Department of Energy following a congressional request in 2010, followed the conclusions developed at the Seismological Society of America meeting that the seismic hazard associated with hydraulic fracturing is extremely low, and that the injection of waste fluids could be linked to increased seismic activity. The committee writing the report called for additional study.
History shows that Oklahoma had naturally occurring earthquakes long before oil and natural gas were discovered in the Sooner State. So, should we be concerned? According to Holland, it is impossible to know the future.
“Certainly this is a very rare occurrence for Oklahoma that has not occurred before in historical times – 150 years,” Holland commented. “Earthquake processes in Oklahoma are very slow – on the order of thousands to millions of years – so we actually know very little about the natural processes of earthquakes. We have seen an increased number of earthquakes, but we have also seen only one earthquake as large as our largest historical earthquake, which was a magnitude 5.5 and occurred on April 9, 1952. Earthquakes have likely always occurred in Oklahoma. We may be seeing the natural earthquake process.”