Texas Drills - then has earthquakes

Many thanks to one of our members (Roger) for this heads up!

Fracking - are these earthquakes related to recent fracking activity in TX? Seems odd they had no earthquakes in the last 140 years and suddenly, after drilling starts so do the quakes!

http://news.yahoo.com/s/ap/20090612/ap_on_re_us/us_texas_earthquakes_drilling

CLEBURNE, Texas – The earth moved here on June 2. It was the first recorded earthquake in this Texas town's 140-year history — but not the last. There have been four small earthquakes since, none with a magnitude greater than 2.8. The most recent ones came Tuesday night, just as the City Council was meeting in an emergency session to discuss what to do about the ground moving.

The council's solution was to hire a geology consultant to try to answer the question on everyone's mind: Is natural gas drilling — which began in earnest here in 2001 and has brought great prosperity to Cleburne and other towns across North Texas — causing the quakes?

"I think John Q. Public thinks there is a correlation with drilling," Mayor Ted Reynolds said. "We haven't had a quake in recorded history, and all the sudden you drill and there are earthquakes."

At issue is a drilling practice called "fracking," in which water is injected into the ground at high pressure to fracture the layers of shale and release natural gas trapped in the rock.

There is no consensus among scientists about whether the practice is contributing to the quakes. But such seismic activity was once rare in Texas and seems to be increasing lately, lending support to the theory that drilling is having a destabilizing effect.

On May 16, three small quakes shook Bedford, a suburb of Dallas and Fort Worth. Two small earthquakes hit nearby Grand Prairie and Irving on Oct. 31, and again on Nov. 1.

The towns sit upon the Barnett Shale, a geologic formation that is perhaps the nation's richest natural gas field. The area is estimated to have 30 trillion cubic feet of recoverable gas and provides about 7 percent of the country's supply.

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From: Chapter 12 of, State of Texas Hazards Analysis, by the Governor's Division of Emergency Management, Department of Public Safety, Austin, Texas, 1998.

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.