Whole lotta shakin’ going on...

Earthquake activity here in Texas is something we seldom hear about, but there have been multiple recent reports of small quakes in North Texas. The seismic activity is monitored by the U.S. Geological Survey offices.

Last month a small quake centered in an undeveloped part of North Arlington. It registered 3.3 on the Richter Scale, and was felt mainly in Bedford, Euless and Irving. Smaller aftershocks were felt in the afternoon, but none as strong as the original. DFW airport and the Trinity Railway Express acknowledged the quake, but stated the tremor had no impact on transportation services.

On Tuesday, June 2, a 2.8-magnitude quake hit the North Texas town of Cleburne, 40 miles south of Fort Worth. Then, less than a week later, two more tremors were reported in that same area. Calls began to come in to the Cleburne police on Sunday, June 7, just before 6 p.m., and the USGS confirmed the quakes, the larger of which registered 2.6-magnitude. It was felt in Cleburne, Rio Vista, Bedford and Grandview, but there were no reports of damage or injuries.

A CBS News 11 report quoted a UT Dallas Geosciences professor, Dr. John Ferguson, as stating that natural gas drilling could be the cause of the quakes. According to Dr. Ferguson, "It's possible the induced seismicity is associated with gas production. This wouldn't be unexpected by earthquake seismologists."

Cleburne experienced a fourth quake on Tuesday. It registered 2.6 and city officials called an emergency meeting with a geologist. An hour before the meeting was to take place, a fifth tremor occurred, registering 2.1. Prior to last week, Cleburne had never registered even one quake in 142 years.

Experts say it is not unusual for quakes to occur in groups, but note that this grouping IS unusual because they all appear to come from almost the exact same spot.

Can the natural gas drill ing be responsible? The region sits upon a geologic formation known as the Barnett Shale, perhaps the nation’s richest natural gas field. It is estimated to have 30 trillion cubic feet of recoverable gas. Thousands of wells have been drilled in the area over the past five years, and Cleburne is at the center of that activity. There are over 200 wells within 30 square miles of the city.

By comparison, the Leon County Appraisal District claims 516 gas wells in this county. Buffalo ISD Tax Accessor Carolyn Ballard identified 173 gas wells in the school district, which includes 99 in Leon County and 74 wells in Freestone County.

Natural gas wells are drilled with a process called “fracking” -- hydraulic fracturing which uses a high pressure water mix to crack open gas-bearing rock. The oil industry generally denies that any evidence links their drilling to increased earthquake activity. Geologists stop short of calling it a definite, direct correlation, but Cliff Frohlich, a senior research scientist at the Institute for Geophysics at the University of Texas at Austin and author of Texas Earthquakes suggests that “most reasonable people with earthquake training probably would say they are related to the gas production.” A geology professor at UT Arlington counters that natural gas drilling is unlikely to contribute to tremors because the two take place at different depths.

Most earthquakes that cause damages are generally about twice as powerful as the tremors which have occurred around Cleburne. So far no damages nor injuries have been reported. They have only rattled dishes and windows -- and the nerves of the Texas residents.