If the earthquakes are occurring near injection wells, they plan to study that potential link, according to the head of the research team.
A group of SMU and University of Texas at Austin researchers have produced two studies since 2009 indicating a possible link between the outbreaks of small earthquakes in North Texas’ Barnett Shale area since 2008 and some injection wells used to dispose of oil and gas drilling waste.
Though the USGS says studies suggest that the actual hydraulic fracturing process is rarely the direct cause of felt earthquakes, U.S. geologists say activities that have induced felt earthquakes in some geologic environments have included impoundment of water behind dams, injection of fluid into the earth’s crust, extraction of fluid or gas, and removal of rock in mining or quarrying operations.
In the south-central states of the U.S., a significant majority of recent earthquakes are thought by many seismologists to have been human-induced, according to a statement posted on the USGS website below information on the recent local earthquakes.
According to the USGS, wastewater disposal appeared to have induced the 5.6-magnitude earthquake in central Oklahoma in 2011 that damaged more than a dozen homes.
The average number of magnitude-3.0 or larger earthquakes that occurred each year from 1975 to 2008 in the Oklahoma City region was one to three, according to the team of U.S. geologists studying the issue. However, since 2009, that average has grown to around 40 earthquakes per year.
State geologists, however, disagreed. The Oklahoma Geological Survey laid out reasons they believe the earthquakes were due to natural causes.
State Rep. Phil King told the Mineral Wells Index that he was skeptical that oil and gas activity may be prompting the earthquakes.
Concerned the environmental community would try to use the issue to shut down oil and gas production in North Texas, King said he is insistent that there be definitive scientific evidence, rather than just correlations and rhetoric.