Dallas area has suffered almost 40 small earthquakes since the beginning of the year
Study says oil, gas activities "most likely" responsible for area's earthquakes in 2013, 2014
Some experts caution that a definitive connection has not been established and further study is needed
Jim and Gail Wells have lived in the upscale Las Colinas area of Irving, Texas, for 14 years.
Nestled between Dallas and Fort Worth, they love their quaint neighborhood for its custom homes amid rolling hills and large trees.
One of the neighborhood’s newer features is a spate of seismic activity.
According to the U.S. Geological Survey, the Dallas area has suffered almost 40 small earthquakes (magnitude 2.0 or higher) since the beginning of this year, the latest a magnitude-2.7 quake near Farmers Branch on Saturday. Many of the epicenters were recorded in Farmers Branch and Irving, with a couple to the south in Venus.
“The quakes don’t sound like much to somebody from California,” Jim Wells told CNN. “But when you are sitting right on top of them, they are more than noticeable. They will shake the entire house, and you have no doubt about it when you have gone through it. We have in my home perhaps 100 or more wall hangings, pieces of art – prints, etchings, oil originals – and none of them are hanging straight.”
On January 7 and 8, Irving experienced 11 earthquakes in about 24 hours. During one of those quakes – a magnitude 3.6 – Gail Wells says the rattling and shaking were so intense it knocked her off the sofa.
Susan Hough, a seismologist at the USGS and the California Institute of Technology, says the epicenter of these types of earthquakes would produce “average-to-high shaking intensities close in, but low intensities” about six miles out.
The Wells’ home sits less than a mile from the epicenter of some of the Irving quakes, and they say they’ve felt at least 15 of them this year. Though there hasn’t been “serious” damage yet, Jim Wells is worried there will be if the quakes continue.
“I don’t think that there is much doubt that there will eventually be damage to the pier and beam structures. There should be damage to the brick facades should it continue, and, of course, damage to the sheet rock and damage to the house,” he said. “You are continuously waiting for the other shoe to drop. You’re concerned that there is going to be another one.”
Since 2008, the northern region of Texas experienced four swarms of earthquakes, more 130 temblors in all.
Concentrated within the Dallas metro area, the frequency of this activity has dramatically increased this year. There were 25 small quakes in January alone.
Most are small, but for an area that the USGS says had only one recorded earthquake in the 58 years before 2008, the uptick has many in the community concerned.
Hough, who has studied seismic activity for years, says the shaking pattern “fits the mold of induced quakes.”
To translate: the seismic activity could be a result of human activity, namely the disposal of a byproduct of hydraulic fracturing called “flowback water.”
Officially, the cause of the earthquakes is inconclusive, according to the USGS, but on Tuesday, a Southern Methodist University-led research team found that in Azle and Reno, towns northwest of Fort Worth, the oil and gas activities in the vicinity were “most likely” responsible for several earthquakes in late 2013 and 2014.
“While some uncertainties remain, it is unlikely that natural increases to tectonic stresses led to these events,” head researcher Heather DeShon of SMU wrote in the report.
This findings were made possible by a “first-of-its-kind” modeling study that “allowed the SMU team to move beyond assessment of possible causes to the most likely cause identified in this report,” it said.
This new data helps clarify the locations of the faults that are the sources of the earthquakes, SMU geophysicist Brian Stump said.
Stump echoed comments made by DeShon earlier this year, explaining that the pattern and position of many of the quakes form a linear trend.
“In order to have an earthquake with the size 3.6 magnitude, there has to be a fault,” she said.
Stump and DeShon say they need more time to monitor activity and “explore the possible mechanisms for these earthquakes.”
George Choy, a USGS research geophysicist, isn’t ruling out that wastewater wells or the injection of fluid into the Earth’s crust during fracking can cause the ground to shake, but he isn’t ready to declare it a fact yet.
“There just isn’t enough evidence to support the claim yet in this case,” Choy said. “I don’t think that has been proven yet. There are some nearby wells that have been inactive for a while. The connection has not been established, but we cannot rule them out. … We cannot make a correlation with any wells without knowing their history.”
Researchers face challenges obtaining the information they need, Choy said, “since many of (the wells) are privately owned, digging into that history can often prove challenging.”
The group that holds key details is the Texas Railroad Commission, which hired seismologist Craig Pearson in April 2014 to help it review well permits, analyze seismic data and assist SMU’s DeShon and Stump.
In a statement to CNN, the commission said, “At this time, there is no definitive link between oil and gas activities in Texas and seismic events” and the commission “has taken numerous, proactive steps on this issue as research is developed in this area.” The commission will continue to help researchers, local governments and industry to nail down information that may advance their studies, it said.