Environmental groups released a report Thursday intended to return public attention to earthquake risks associated with underground injection activity in oilfields near Bakersfield and other California population centers.

Without pointing to any seismic activity caused by hydraulic fracturing, acidization or wastewater disposal in the state, the report sounds an alarm that these operations pose special dangers in California because they often take place near earthquake faults.

It says 54 percent of active or new wells in the state are located within 10 miles of a recently active fault, and 6 percent lie within just one mile of such a fault. It points to many such situations in Kern County.

The report is not the first to link oil work with seismic activity. Its release is the latest attempt by anti-oil activists to build support for a statewide ban on the controversial technique known as hydraulic fracturing, or "fracking."

People who have studied the issue don't generally blame seismic activity on fracking, which injects water, sand and sometimes toxic chemicals underground at high pressure to free up hard-to-reach oil and gas deposits. Acidization is a similar procedure using caustic chemicals in place of water.

But as the report points out, expectations for increased use of fracking in and around the southern Central Valley would entail greater need to dispose of tainted water and other substances that come up along with petroleum. It is that disposal work, done by underground injections, that researchers have linked to seismic activity in other states.

"We've known for decades that wastewater injection increases earthquake risk," report co-author Jhon Arbalaez wrote in a news release. "Since Gov. (Jerry) Brown resolutely refuses to learn from other communities' experience with fracking across the country, our only option to protect California families is to prevent fracking altogether."

The industry maintains that such a ban would be going too far. Rock Zierman, CEO of the California Independent Petroleum Association trade group, noted that oil companies are required by federal law to examine how injected water will react with any nearby fault lines, and that their analysis is reviewed by state oil engineers.

"That is probably why in CA we have re-injected billions of gallons of water without any negative impact on seismicity," he wrote in an email.

A senior state oil regulator said his office is reviewing the report, but that its "assumptions and conclusions" should be examined in a peer-review process. He further noted that, besides evaluating subsurface geology before conducting underground disposal work, oilfield operators regulate injection pressures "to avoid creating problems with seismicity."

"Other states with a less extensive history of managing wastewater or the vast amounts of brackish 'produced water' typical in California production may not have similar requirements in place," the regulator, state Department of Conservation Chief Deputy Director Jason Marshall, wrote in an email.

A state law signed by Gov. Brown last year requires oil companies to evaluate all active and inactive faults near any proposed fracking or acidization operations. The law also calls for monitoring for and reporting seismic activity for 60 days after such operations.

The report released Thursday was produced by the environmental activist groups Earthworks, the Center for Biological Diversity and Clean Water Action.

Asserting that California regulators have failed to study seismic risks of oilfield work, the authors pointed to studies concluding that Oklahoma has experienced a surge in earthquakes amid recent drilling in the state.

According to the U.S. Geological Survey, Oklahoma had only one to three magnitude 3.0 quakes or larger from 1975 to 2008. But between 2009 and mid-2013, the agency noted, the average shot up to about 40 such earthquakes per year.