WASHINGTON – Federal scientists forecast that Oklahoma will continue to have the nation’s biggest man-made earthquake problem but 2017 probably won’t be as shaky as recent years.

In February, the USGS reported six earthquakes in Kansas.

The strongest measured 3.3 on February 22, and was centered four miles northeast of Anthony in Harper County. Another 3.3 quake hit just north of the Oklahoma State line in Sumner County on February 13. A 2.6 quake shook Sumner County on Sunday morning.

In its annual national earthquake outlook, the U.S. Geological Survey reported this week that a large portion of Oklahoma and parts of central California have the highest risk for a damaging quake this year: between 5 and 12 percent.

Seismologists say Oklahoma’s problem is triggered by high volume ground injections of wastewater from oil and gas drilling.

USGS seismic hazard chief Mark Petersen says Oklahoma’s recent regulation wastewater injection is starting to work, so scientists slightly reduced Oklahoma’s risk this year.

– The AP contributed to this report.