What may be the first class-action suit against oil and gas companies for unleashing earthquakes is working its way through the federal courts in Arkansas. The suit stems from a "swarm" of earthquakes as strong as magnitude 4.7 that rattled the northern part of the state. The quakes prompted state officials last summer to ban drilling waste disposal wells in a 1,150-square-mile area. Four wells ceased operations. The people who brought the suits and their attorneys say the companies knew about the risk of earthquakes from their operations but did not do enough to prevent them.