This map layer contains locations and information on faults and associated folds, in the United States, that are believed to be sources of significant earthquakes (those of magnitude 6 or greater) during the past 1,600,000 years. This layer is part of the 1997-2014 edition National Atlas of the United States.These data are intended for geographic display and analysis at the national level, and for large regional areas. The data should be displayed and analyzed at scales appropriate for 1:250,000-scale data. No responsibility is assumed by the National Atlas of the United States in the use of these data.