The U.S. Geological Survey (USGS) said a pair of earthquakes, including one that registered 4.2 magnitude on the Richter scale, hit central Oklahoma late Monday and early Tuesday.
According to the USGS, the 4.2-magnitude temblor struck first, at 11:53 p.m. CDT on Monday. The second quake registered 3.6-magnitude and struck at 5:19 a.m. CDT on Tuesday. The epicenters for both earthquakes was northeast of Crescent, OK -- the first about 3.1 miles away, the second about 2.5 miles away. No injuries or damage was reported from either quake.
On Monday, the USGS issued a report that said six states, including Oklahoma and Texas, were at the greatest risk for human-induced seismic activity (see Shale Daily, March 28).
Earlier this month, the Oklahoma Corporation Commission's Oil and Gas Conservation Division (OGCD) ordered more than 400 wastewater injection wells targeting the Arbuckle Formation to reduce their disposal volumes by 40% below 2014 levels over the next two months (see Shale Daily, March 7). The OGCD also expanded its "area of interest" in the state, effectively placing restrictions on more than 100 additional disposal wells in areas that have not yet recorded major earthquake activity.
The OGCD began ordering operators to either shut down or curtail intake volumes at injection wells in March 2015, shortly before scientists with the Oklahoma Geological Survey (OGS) attributed the increase in seismic activity to injection wells targeting the Arbuckle Formation, which closely overlies the crystalline basement (see Shale Daily, April 22, 2015; April 2, 2015). The OGS said the disposal of extremely salty water -- a byproduct of oil and gas production, not the mostly freshwater used for hydraulic fracturing -- is responsible for the quakes (see Shale Daily, Jan. 5).