A gas flare burns at a fracking site in rural Bradford County, Pennsylvania. The U.S. Geological Survey is set to release findings Wednesday that a \A gas flare burns at a fracking site in rural Bradford County, Pennsylvania. The U.S. Geological Survey is set to release findings Wednesday that a "remarkable" increase of quakes in the U.S. midcontinent since 2001 is "almost certainly" the result of oil and gas production. (Reuters)

Two separate studies are providing insights into the earth-shaking consequences of the controversial gas extraction process known as fracking.

Both studies confirm that processes linked to the extraction of oil and gas through hydraulic fracturing, or fracking, can trigger manmade earthquakes. Fracking involves blasting water, sand and chemicals deep into the ground to fracture rock to obtain oil and natural gas.

Energy companies are increasingly using the technique across Canada, where there is already regular seismic activity and an ever looming threat of various sized tremors.

The U.S. Geological Survey is set to release its findings Wednesday that a "remarkable" increase of quakes in the U.S. midcontinent since 2001 is "almost certainly" the result of oil and gas production. However, the lead author of the report, Bill Ellsworth, emphasized in an interview with the U.S. televison network CNBC that the earthquakes aren't caused by the fracking process itself that is used to extract the gas. Rather, earthquakes have been linked to the injection of wastewater produced during fracking back into the ground in order to dispose of it.

U.K. experts, meanwhile, point to a study released Monday that found recent earthquakes in northwest England were caused by fluid injection into a nearby fault zone as evidence fracking can be safe when conducted by responsible operators.

The consultants' report, commissioned by the U.K. government and published on Tuesday recommends that fracking should be halted temporarily if there is a tremor greater than magnitude 0.5 on the Richter scale. Cuadrilla Resources, a company that halted its fracking activities in northwestern England following tremors of magnitudes 2.3 and 1.5 in April and May last year, has said that is acceptable.

Opposition to fracking has ramped up since the release of the 2010 documentary "Gasland," which shows residents of small town Colorado setting alight tap water they charge was soured by nearby oil industry activity.

Corrections and Clarifications

  • According to the USGS study, the earthquakes are linked to the disposal of wastewater produced during fracking, not the fracking process itself, as previously reported. Thursday, April 19, 2012 | 2:41 p.m. ET
With files from the Associated Press