A lawsuit claims that Oklahoma’s great increase in earthquake activity has been caused by pumping waste from drilling operations back underground. The suit involves the largest measured quake in the history of the state, a 5.6 tremor that happened in Prague, east of Oklahoma City in November 2011. As the volume of drilling waste pumped underground has grown, the number of earthquakes with magnitude 3 or higher has increased. In particular, as the drilling has intensified along the northern border, the quakes have followed. The Prague 5.6 magnitude quake in 2011 had one 4.8 magnitude foreshock and one 4.8 magnitude aftershock.