Minor quakes from fracking operations may trigger larger tremors: study

SAN FRANCISCO, Dec. 12 (Xinhua) -- Small earthquakes induced by hydraulic fracturing, also called fracking, a technology employed in oil and gas production, are likely to trigger bigger tremors in future, a new study shows.

The study, conducted by a team of researchers led by geoscientists from U.S. Stanford University and published in a recent edition of the Journal of Geophysical Research, examined data about seismic activities in Arkansas state in the southeastern region of the United States, where two larger aftershocks followed a minor quake between 2010 and 2011.

The Stanford scientists devised a way of detecting thousands of faint, previously missed earthquakes triggered by fracking.

The drilling technique can be used to monitor seismic activities in fracking operations, in which high-pressure fluid is injected underground to crack open rocks and release the natural gas trapped inside.

During the drilling process, the cracking of rocks may produce tiny earthquakes that are typically too small to be detected.

The Stanford researchers worked out an advanced data-mining algorithm to conduct a retrospective analysis of seismic activity in Arkansas.

The algorithm uses earthquake-pattern recognition to generate detailed records of seismicity.

The researchers found that there were more than 14,000 small, previously unreported earthquakes in Arkansas, and most of them were the direct result of fracking operations at 17 of the 53 production wells in the area.

In October 2010, a magnitude-4 quake rocked residents near an Arkansas natural gas field, which triggered two larger aftershocks in the following year. They have also subsequently rattled Oklahoma, Texas and other gas- and oil-producing states.

"When earthquakes during fracking operations are larger than expected and persist for weeks, it indicates a high level of stress in that area," said the study's co-author William Ellsworth, quoted by a Stanford press release on Tuesday.

Faults under high stress are unstable and can slip, triggering larger earthquakes, he explained.

He said the algorithm developed by the Stanford researchers offers an efficient, cost-effective method for getting more information out of existing data, so that future decisions can be made to prevent more earthquakes from happening. Enditem