According to the study by the US Geological Survey, the exponential increase in earthquakes that have occurred in Colorado and New Mexico since 2001 is directly linked to the extraction activities of natural gas and oil that began a few years earlier in the two states, in 1994 and 1999 respectively.

When companies began extracting hydrocarbons on a massive scale in these areas, they consequently produced an enormous quantity of wastewater which, pumped underground for disposal, has disrupted the seismic equilibrium of the area between the two states.

According to the same scientists, Colorado and New Mexico were initially considered seismically fairly quiet zones, where only one earthquake above magnitude 3.8 on the Richter scale had occurred over the course of three decades; since 2001, however, at least 16 earthquakes of this magnitude or greater have occurred in the two areas.

In particular, the researchers state that "The increase in earthquakes is confined to the zone of industrial activity, within a radius of 5 kilometres from the wastewater injection wells."

A hydrocarbon extraction plant using fracking in California. Photo © Getty Images

For this specific area, the research finds no "responsibility" attributable to fracking — that is, the pumping of water and chemicals into the ground to extract natural gas and oil — despite the activity being very similar to the disposal of wastewater from conventional hydrocarbon extraction.

However, the scientists acknowledge that both fracking and the underground disposal of wastewater could be linked to the surge in the number of earthquakes in Oklahoma, a state that already broke records with 222 "felt" earthquakes last year.