Waste-water disposal wells used by the oil and gas industry may be responsible for many earthquakes across the US. More than 30 mild intensity earthquakes have been recorded from November to January in North Central Texas.

Researchers from the US Geological Survey have also been investigating links between earthquakes in Kansas, Oklahoma, Ohio and other places to oil and gas activities. USGS seismologist Art McGarr said one thing is quite clear that deep disposal of drilling waste was responsible for some quakes.

Though only few of the disposal wells cause earthquakes to be felt, it cannot be ignored that there are many such wells across the nation and collectively they add to the total seismic hazard.

For now, exact reasons for the same are not known. But one thing that researchers have confirmed is earthquakes have increased in number in the US along with rise in fracking. As per reports, more than 100 earthquakes occurred in a year with magnitude of 3.0 or more than it in the central and eastern U.S. for past four years.

The number sounds to be quite much when compared with just 20 earthquakes taken place in a year between 1970 and 2000. The USGS has stressed that fracking itself can rarely cause earthquake. The issue is about the disposal of the wastewater into wells.

According to the USGS, fracking leads to the production of large amount of wastewater. Wastewater is pumped from deep underground to dispose of it without affecting fresh water. It is the injection that increases the underground pressure and weakens the fault lines and leading to quakes. “Waste water is the dominant cause”, said Gail Atkinson from Western University in London, Ontario.