An expert says earthquakes related to gas drilling

This article appeared the the Dallas Morning News this morning. Some may try to dispute it but at the end of the article is a link to a study done on causes of earthquakes in Texas. Yes, drilling and injecting chemicals and water into the ground have caused earthquakes.

http://www.dallasnews.com/sharedcontent/dws/dn/latestnews/stories/060909dnmetquakes.40620de.html


Cleburne quakes probably related to gas drilling, expert says
10:04 PM CDT on Monday, June 8, 2009
By SHERRY JACOBSON and DAVID TARRANT / The Dallas Morning News sjacobson@dallasnews.com; dtarrant@dallasnews.com
Three small earthquakes that rattled Cleburne in the past six days were probably caused by intense natural-gas drilling, the state's leading expert on earthquakes said Monday.
"Most people would probably conclude if they looked at the data that they would be related," said Cliff Frohlich, associate director and senior research scientist at the Institute for Geophysics at the University of Texas at Austin.
Other scientists, however, were not so certain that any connection could be confirmed.
John Breyer, professor of geology at Texas Christian University, said residents need not worry that the drilling could be causing earthquakes.
"Sometimes these things just happen. It's like the weather," he said. "Sometimes it rains a lot and other times not at all."
The tremors appear to be the first ever recorded in Cleburne, a city of 30,000 about 50 miles southwest of Dallas.
Cleburne sits near the heart of the North Texas Barnett Shale gas field. Since 2001, more than 200 natural-gas wells have been drilled within the city limits.
Surrounding Johnson County has more than 1,000 gas wells.
The three quakes registered magnitudes of 2.3, 2.6 and 2.8, which are considered mild. No injuries or damage was reported in the city.
The tremors were detected Monday morning, Sunday evening and last Tuesday afternoon by the U.S. Geological Survey, which tracks earthquakes around the globe.
Nearly 100 Cleburne-area residents also alerted 911 after feeling tremors during the three quakes.
Residents described the quakes as similar to sonic booms without the deafening sound, or like a large truck rumbling down a nearby street.
"The house shook for about a second or so," recalled Cleburne City Manager Chester Nolen. "But nothing fell off the walls."
Frohlich said he made his connection based on "the characteristics of the earthquakes and the fact that there's been an enormous amount of drilling and injection of fluids in that area for recovery of gas."

Link 'not known'
However, the connection was denied by the Barnett Shale Energy Education Council in Fort Worth, a consortium of gas companies that provides information about natural-gas drilling.
Ed Ireland, executive director of the council, noted that the three Cleburne quakes were reported to have occurred three or four miles beneath the surface, while the drilling occurred about a third of that depth.
"I'm not a geologist," he said. "What I'm told is that there has never been shown to be a concrete relationship between drilling and earthquakes. It's not known."
But UT's Frohlich said scientists can locate the map coordinates of an earthquake a lot better than they can locate its depth.
"When the National Earthquake Information Center reports an earthquake at 5 kilometers, that's really a placeholder – meaning it's a shallow earthquake," he said.
"And they don't know whether it was a half a kilometer or 20 kilometers, because those are all shallow earthquakes."
Frohlich, who co-wrote a 2003 book titled Texas Earthquakes, said he believes oil and gas drilling has caused some Texas quakes.
His book studied 100 earthquakes recorded in the Lone Star State between 1811 and 2000. About a quarter of them were near oil and gas fields, he said.
"In most cases, there weren't earthquakes reported there prior to oil and gas drilling activity," he noted. "And so they would be suspected as possible candidates for being produced by oil and gas."
Further, Frohlich said he suspected that a half-dozen minor quakes detected in North Texas over the past nine months could be linked to natural-gas drilling. Since last October, tremors have been reported in Irving, Grand Prairie, Euless and Dallas.

Not alarmed
Frohlich conceded it might be difficult to make a precise link between the tremors and gas drilling. "It's very hard to determine causes for sure," he said.
In any event, he said, the public should not be overly alarmed.
"They probably pose no hazard," he said. "And I don't see these earthquakes as the kind of thing that lead to bigger earthquakes."
The U.S. Geological Survey considers Texas a low seismic area, compared with such volatile places as California or Alaska.
"Three earthquakes in six days is very unusual for Texas," noted Paul Caruso, a geologist with the agency's National Earthquake Information Center in Golden, Colo.
"What it means we can't really say. Further investigation needs to be done by the state of Texas or the Geological Survey."
Cleburne officials sounded rattled Monday as they considered whether their quakes might not be a natural occurrence.
Mayor Ted Reynolds said he was not ready to blame the widespread drilling for shaking up the community. Still, he called for a study of what might have caused the tremors.
"We will certainly investigate it," he said. "We haven't decided how to do it. But we would be negligent if we didn't."

http://www.ig.utexas.edu/research/projects/eq/compendium/earthquakes.htm?PHPSESSID=cd936f259561eda912004acf9aa66df1#Cause%20of%20Earthquakes

Scroll down and read this paragraph from the above study on causes of Texas Earthquakes

"Finally, some human activities are known to cause or trigger earthquakes. These include the injection of fluids into the earth for waste disposal or petroleum production, and the filling of deep lakes or reservoirs. In Texas, there have been earthquakes associated with oil and gas production at a number of fields. These include the Wortham field in Freestone County, the East Texas and Longview fields in Upshur and Gregg Counties, the Cogdell field in Scurry and Kent Counties, and the Fashing and Jourdanton fields in Atascosa County. None of these quakes have been very damaging or very large; the largest had magnitude 4.7. And, usually petroleum production does not cause earthquakes; in Texas there are more than two thousand oil and gas fields but only about five seem to have generated earthquakes. Nevertheless, wherever there is considerable petroleum production, and especially when there is fluid injection to enhance recovery of to dispose of waste, people should be aware that induced earthquakes are possible."