The U.S. Geological Survey reported at least 9 minor earthquakes since the weekend in Oklahoma, a state wary of the connection between fracking and tremors.

The USGS reported two magnitude-2.8 tremors in Oklahoma early Monday. There were six quakes Sunday, including a magnitude-3.9 quake that hit the town of Waukomis, about 60 miles north of the state capital. A magnitude-5.1 quake was recorded Saturday near Fairview, about 100 miles north of Oklahoma City.

Oklahoma is one of the top five oil production states in the nation, accounting for an average of between 3 percent and 4 percent of the total output in the United States. The U.S. Energy Information Administration last week raised its estimate for total state production by 100,000 barrels per day. EIA's most recent data set show Oklahoma holds about 1.2 million barrels of oil.

Oklahoma reported 907 earthquakes of magnitutde-3 or greater last year, up 54 percent from 2014 and seven times more than recorded in 2013.

In January, Oklahoma Gov. Mary Fallin authorized the use of $1.4 million from state emergency funds to help drive earthquake research at the Oklahoma Corporation Commission and the Oklahoma Geological Survey.

"I'm committed to funding seismic research, bringing on line advanced technology and more staff to fully support our regulators at they take meaningful action on earthquakes," she said.

A study last year from the USGS found the increase in seismic activity in Oklahoma since 2009 may be in part related to activity associated with oil production. The rate of quakes reported in the state since then far surpassed rates from the 20th century.

The USGS said the disposal by the energy industry of wastewater in deep underground wells is potentially leading to more earthquakes.