Seven million people live in seismic risk areas in the United States due to oil and gas exploitation, the National Geological Survey (USGS) reported today.
The technique known as hydraulic fracturing, "fracking" has made many territories of the country become highly prone to seismic events.
"By including events man-made (...) by injection or extraction of fluids, our assessment of earthquake risks has increased significantly in parts of the US," said Mark Petersen, map project manager. USGS seismic hazard.
The states most prone to this phenomenon are Oklahoma, Kansas, Texas, Colorado, New Mexico and Arkansas. Of these, Oklahoma and Texas are where the greatest number of inhabitants are at risk.
However, a spokesperson for the National Geological Service reported that the study carried out by the institution shows that "many more parts of the country have significant possibilities of registering one of these earthquakes in the next year" when adding the areas of natural risk prone to earthquakes like California, the region where the San Andrés tectonic fault is found.
Thus, between 1973 and 2008, in the United States there was an average of 24 earthquakes of magnitude 3 or more per year, but between 2009 and 2015, the average was 318, as reported by the USGS.
"Fracking" is an extraction technique that injects a mixture of water and chemicals into the subsoil at high pressures to break the porous rocks that store fuels and thus release them. The boom in hydraulic fracturing is behind the energy “boom” in the US.
During 2010, Oklahoma, where a large number of fracking wells are concentrated, registered three earthquakes greater than magnitude 3 on the Richter scale; but in 2015, 907 were registered.
In February of this year it suffered the third largest earthquake in its history, with a magnitude of 5.1 on the Richter scale, fortunately the earthquake did not leave victims or material damage.
These statistics have made that in early March, the Oklahoma Corporation Commission (OCC) reported that the volume of wastewater injections will be reduced by 40 percent in 400 wells within the state.