HOUSTON (Reuters) - Oklahoma is imposing guidelines to reduce the risk of earthquakes caused by hydraulic fracturing in its oil-rich shale formations, the first rules in the state to target the controversial production technique.

The guidelines are aimed at the South Central Oklahoma Oil Province (SCOOP) and Sooner Trend Anadarko Basin Canadian and Kingfisher counties (STACK) formations, which are anticipated to account for most new oil and gas activity in the state, authorities said on Tuesday.

The moves by the Oklahoma Corporation Commission's Oil and Gas Conservation Division and the Oklahoma Geological Survey came as earthquakes in the state have risen sharply since the shale boom and the use of hydraulic fracturing, or fracking.

The guidelines, which go into effect immediately, include provisions that require producers to implement mitigation plans following an earthquake of magnitude 2.5 or more and to suspend operations following a quake of magnitude 3.5 or greater.

While the guidelines are technically voluntary, the Oklahoma legislature this year gave the Oklahoma Corporation Commission powers to make compliance mandatory.

“We regard these as a starting point, and the producers have been fully cooperative,” said Matt Skinner, public information officer for the Oklahoma Corporation Commission.

So far, directives have focused on curbing use of injection wells for the disposal of saltwater, a normal byproduct of production.

Oklahoma experienced almost 900 earthquakes magnitude 3.0 or greater in 2015 versus just two or three a year before 2009.