Mealey's (June 11, 2018, 9:50 AM EDT) -- TULSA, Okla. — The Pawnee Nation of Oklahoma on May 17 sued two hydraulic fracturing companies in Oklahoma federal court, contending that they disposed of wastewater and introduced contaminants into the natural environment that caused “unnatural seismic activity” (Pawnee Nation of Oklahoma v. Eagle Road Oil LLC, et al., No. 18-263, N.D. Okla.)....