Four minor earthquakes were reported in and around the shale reserve basins in Oklahoma in the last 24 hours, the U.S. Geological Survey found. The USGS recorded three minor tremors, including two near the metropolitan area of Oklahoma City, inside state borders and one less than 100 miles across the border in Kansas. The largest of the tremors was the 3.5-magnitude quake recorded about 20 miles east from Oklahoma City, the state’s capital. A March report from the USGS found central U.S. states have experienced a dramatic increase in seismic activity over the past six years. Between 2009 and 2015, there have been an average 318 quakes in the region, against an average of 24 in the 35 years ending in […]