OKLAHOMA CITY (AP) — Geologists say they may have found previously unmapped faults in Oklahoma that could be contributing to a sharp increase in induced earthquakes in the state.

The possible faults were found in a study by the U.S. Geological Survey and the Oklahoma Geological Survey that focused on areas around earthquakes of magnitude 5.0. Many of the earthquakes weren't on known faults.

Oklahoma Geological Survey Director Jeremy Boak said Tuesday the apparent faults extend from what appeared to be the end of mapped faults directly to areas where many quakes occurred.

A report in Geophysical Research Letters by U.S. Geological Survey scientists says data indicates the suspected faults were activated by wastewater injection.

The process oil and natural gas producers use to dispose of wastewater has been linked to many Oklahoma earthquakes in recent years.