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Quaternary Fault Lines

2025 - Homeland Infrastructure Foundation Level Data HIFLD


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ABSTRACT
The Quaternary Fault and Fold Database contains the results of thousands of scientific assessments of faults and associated folds in the United States that demonstrate geologic evidence for coseismic surface deformation in the Quaternary (the past 1,600,000 years). The Quaternary Fault and Fold Database includes information on the age of the most recent coseismic surface deformation, relative rates of activity, fault geometry, sense of movement, and citations of pertinent literature. Much of the information in the database is based on paleoseismology, which is the geologic study of prehistoric earthquakes. Paleoseismology combines well-established geologic practices such as trenching with archeological-style analysis to determine the time and magnitude of ancient earthquakes. These studies extend the historical earthquake record by hundreds of thousands of years and are indispensible in calculating future seismic hazard posed by the thousands of faults in the United States. The data are accessed through search pages or an interactive map service. The work of the USGS and its cooperators in developing this database is only one part of the ongoing USGS efforts to protect lives and property from future earthquakes throughout the United States.