U.S. government scientists have identified 17 areas in eight states that have seen an increase in earthquakes triggered by human practices.
Earthquake activity in the central and eastern United States has increased significantly since 2009 and this has been linked to the disposal of oil and gas wastewater by injecting it into deep wells.
The new report by the U.S. Geological Survey (USGS) offers a comprehensive assessment of the hazard levels associated with induced earthquakes in parts of Alabama, Arkansas, Colorado, Kansas, New Mexico, Ohio, Oklahoma and Texas.
The report coincided with a statement released this week by the Oklahoma Geological Survey (OGS), which officially recognized for the first time the link between oil and gas wastewater disposal and the record number of earthquakes recorded in the state in recent years.
“The OGS considers it very likely that the majority of recent earthquakes, particularly those in central and north-central Oklahoma, are triggered by the injection of produced water in disposal wells,” the state agency said.
Both agencies stressed that the primary cause of triggered seismicity is believed to be wastewater disposal, rather than the hydraulic fracturing process.
“Wastewater injection increases the underground pore pressure, which may lubricate nearby faults thereby making earthquakes more likely to occur,” USGS stated. The federal agency also pointed out, however, that although the disposal process has the potential to trigger earthquakes, most wastewater disposal wells do not produce felt earthquakes.