Active fault

An active fault is a fault that has slipped during the present seismotectonic regime and is therefore likely to have renewed displacement in the future.

The fault activity may be indicated by historic geologic seismologic geodetic or other geophysical evidence of activity. The rates may vary from very low with long recurrence intervals to very high with short recurrence intervals.
The most recent offset along faults with long recurrence intervals May either be recent or ancient. Some workers compare active faults with active volcanoes which show either historic or geologically recent activity or are dormant but with the potential for future activity. Definitions generally include a time indication of either the most recent offset or a recurrence interval. The most widely used definition in current engineering practice is for faults with evidence of Holocene displacement (approximately the last 10 000 years). Some definitions include the connotation that active faults may move or have offsets during the life of man-made structures but most workers prefer to define the term independently of applications or man-made structures.

Slemmons and McKinney (1977)