Daily Mail Reporter: Oklahoma Earthquake Caused by Energy-Drilling Process

The reason behind last week's earthquake in Oklahoma is still eluding scientists, though they think it might have been connected to the growing use of hydraulic "fracturing." The process, commonly called 'fracking', pumps water into the earth, in an effort to release natural gas and oil. Scientists first noticed that small earthquakes in Oklahoma, with magnitudes between 1 and 2.8 near a fracking site in August, though they did nothing to stop its usage: Researchers said there was not enough evidence to say with 'a high degree of certainty' that the small earthquakes were caused by fracking. The small tremors were felt by residents, but were nothing compared to the 5.6 magni -tude earthquake that struck the Sooner State last Saturday evening. Scientists are puzzled by the recent seismic activity. It appeared the latest quake occurred on the Wilzetta fault, but researchers may never know for sure. Earthquakes that hit east of the Rocky Mountains are harder to pinpoint because the fault systems are not as well studied as major faults like the San Andreas in California. Arkansas also has seen a big increase in earthquake activity, which residents have blamed on injection wells. Natural gas companies engaged in hydraulic fracturing, or fracking, use fluid to break apart shale and rock to release natural gas. Injection wells then dispose of the fluid by injecting it back into the ground. There are 181 injection wells in Oklahoma.