OKLAHOMA CITY — Scientists may have found previously unmapped faults in Oklahoma that could be contributing to a sharp increase in induced earthquakes in the state, according to a report on a study that used magnetic imaging to explore the rock formations below the earth's surface.

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

"This study really gave us some new interesting information about the orientation of faults," Boak said. "You can see something in the grain and structure (of the rock) that continues that fault," it's deeper.

The Oklahoma agency and the U.S. Geological Survey studied areas where four quakes of magnitude 5.0 or stronger have struck since 2011. A report by lead author Anji Shah of the U.S. Geological Survey was published in Geophysical Research Letters .