Drilling might be culprit behind Texas earthquakes

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% of the country's supply.

The drilling's economic impact has been significant, because gas companies pay signing bonuses and royalties to property owners for the right to drill beneath their land. Signing bonuses climbed to around $25,000 an acre at the boom's peak.

Cleburne agreed to lease the mineral rights in the earliest stages of the frenzy, receiving a modest $55 an acre for 3,500 acres of city land. There are about 200 drilling sites in Cleburne, and it is not unusual to see cattle chewing grass in the shadow of gas pipes.