An Ohio injection well used to dispose of wastewater from oil and natural gas drilling by shooting the hazardous liquid deep underground may be responsible for causing a series of 11 minor earthquakes that shook the Youngstown area over 2011, the most recent of which occurred on Dec. 31, according to a report from The Associated Press.

The wastewater dumped into the injection wells is the byproduct of drilling operations, particularly hydraulic fracturing, which involves extracting gas from beneath the earth by injecting huge quantities of water, sand and chemicals underground to break up shale rock and release natural gas. The AP reports thousands of gallons of such wastewater was injected daily into a Youngstown well that opened in 2010, a process that was stalled on Dec. 30 after its owner, Northstar Disposal Services LLC, agreed to suspend operations while authorities investigated links between the well and the region's unusual seismic activity. The next day, the year's 11th quake occurred.

The earthquakes will trickle on as a kind of a cascading process once you've caused them to occur, John Armbruster, a Columbia University seismologist, told the source, adding that he expects more earthquakes to occur in the area. This one year of pumping is a pulse that has been pushed into the ground, and it's going to be spreading out for at least a year.

The Dec. 31 earthquake, as well as the seismic event preceding it on Dec. 24, took place within 100 yards of the Youngstown injection well. Although Ohio state officials reportedly claimed the seismic activity was the result of injecting wastewater near a fault line -- causing enough pressure to trigger a low-level quake -- the state announced that four inactive wells within a five-mile radius of the Youngstown well will remain closed.

Although both the Ohio House of Representatives and Senate have introduced legislation to suspend fracking in the state until the U.S. Environmental Protection Agency concludes a study on the process' impact on water resources, the Cleveland Plain Dealer reports both bills have been stalled in the state legislature.

The Ohio earthquakes are far from the first to be connected with drilling for oil and natural gas. While injection wells are also suspect in quakes that occurred in Ashtabula, Ohio, as well as in Arkansas, Colorado and Oklahoma, some scientists suggest a rush of unusual seismic activity may be caused by hydraulic fracturing, better known as fracking.

One study released by the Oklahoma Geological Survey last August found that fracking may have triggered a series of almost 50 small earthquakes on Jan. 19 in a rural area near Elmore City. While the study did not conclusively determine whether the fracking wells actually caused the earthquakes, the authors pointed out the majority of the earthquakes occurred within 3.5 kilometers of a well located in the southern portion of the state's Garvin County.

In addition, the authors of the report write that seismologists suspected earthquakes could be linked with hydraulic fracturing as far back as 1978, when 70 earthquakes occurred in a 6-hour period in Oklahoma's Carter and Love Counties. A second case ensued in Love County in 1990, when 90 earthquakes reportedly occurred after fracking wells were implemented in the area.

However, despite the speculation, the report states that uncertainties in the data make it impossible to say with a high degree of certainty whether or not these earthquakes were triggered by natural means or by the nearby hydraulic-fracturing operation.

The possible connection between fracking and earthquakes is not limited to the U.S. In May, the British Geological Survey made headlines when it reported it is highly probable that two small earthquakes that occurred near Blackpool were caused by hydraulic fracturing. The report, financed by the U.K. energy company Cuadrilla Resources Ltd., specified the geological circumstances surrounding those quakes was rare and that the strongest possible tremor that could have resulted would not have been strong enough to pose any danger.

The report showed the pumping operations we were involved in triggered the events, Cuadrilla CEO Mark Miller told BusinessWeek in November. It also gave us recommendations for how to proceed that will mitigate that risk. We can change the volume of the fluids as well as put in an early warning system that would give us the ability to terminate drilling very early.