A report by a US government geologist says the number of earthquakes in the central part of the country rose spectacularly near where oil and gas drillers disposed of wastewater underground.
Scientists at the US Geological Survey say the average number of mid-continent earthquakes of magnitude 3 or greater increased to six times the 20th-century average last year.
They say the wastewater generated by fracking - or hydraulic fracturing - and other extraction processes may play a role in causing faults to slip, causing quakes.
A co-author of the study, Arthur McGarr from the Earthquake Science Centre in California, told Checkpoint the water lubricates the fault.
Mid-continent states include Arkansas, Colorado, Oklahoma, New Mexico and Texas.