DENVER (AP) — Recent earthquakes in Colorado and elsewhere were induced by a drilling procedure to dispose of wastewater, and regulators in Colorado have started to look for seismic risk in permit reviews, federal regulators said.

The Denver Post reported Tuesday that Colorado drilling regulators said more study is needed on the link between drilling waste disposal and the uptick in earthquakes. But, nevertheless, regulators are looking at permits to analyze earthquake risk.

A report due this week at a gathering of the American Geophysical Union says an increase in earthquakes on the Raton Basin in Colorado, northern New Mexico and elsewhere is tied to disposal wells where oil and gas drilling wastewater is injected. Drilling companies use disposal wells to bury brine water and chemical waste that result from hydraulic fracturing, or fracking.

A 5.3-magnitude earthquake near Trinidad last year triggered minor rockslides, toppled chimneys and cracked walls. No one was hurt. The quake followed injection of 4.9 million cubic meters of wastewater

And on Tuesday, a 3.9-magnitude earthquake was recorded about 20 miles west of Cokedale, near the New Mexico border. The temblor was reported by the National Earthquake Information Center in Golden, but no damage was immediately reported.

The wastewater report should prompt discussion of disposal wells, said U.S. Geological Survey scientist Justin Rubinstein, co-author of the report.

"This is a societal risk you need to be considering," Rubinstein told The Post.


A USGS team based in Menlo Park, Calif., found that the quake in Colorado and a damaging 5.6-magnitude quake in Oklahoma both were induced by disposal of fracking waste underground.

From 1970 until 2001, five quakes of magnitude 3 or higher were recorded on the Raton Basin. Scientists counted 95 quakes of that magnitude between 2001 and 2011 and concluded that oil and gas operations caused the majority, if not all, of the quakes since 2001.

While the evidence is convincing that deep burial of drilling waste can trigger quakes, it also appears that few of the 40,000 disposal wells nationwide have done so, Rubinstein said.

"But I don't think blowing this off is a good idea,