The age of fault slip refers to the time period when the fault is believed to have last moved. The age is
expressed in terms of the Geologic Time Scale. Generally, the older the activity on a fault, the less likely
it is that the fault will produce an earthquake in the near future. For assessing earthquake hazard, usually only
faults active in the Late Quaternary or more recently are considered. These include the following three
non-overlapping time periods:

Historic. Refers to the period for which historical records are available (approximately the past
200 years in California and Nevada).

Holocene. Refers to a period of time between the present and 10,000 years before present. Faults of this age
are commonly considered active. For the purpose of classifying faults, C.W. Jennings* defined Holocene to
exclude the Historic; that is, from 200 to 10,000 years before the present). More about the Holocene

Late Quaternary. Refers to the time period between the present and approximately 700,000 years before the
present. Here too, for the purpose of classifying faults, Jennings defined Late Quaternary to exclude the
Holocene and the Historic. More about the Quaternary

*"Preliminary Fault Activity Map of California" by C.W. Jennings (1992, California Division of Mines and Geology
Open-File Report 92-03). This map has been superseded by Jennings, C.W., 1994, Fault activity map of California
and adjacent areas, with locations and ages of recent volcanic eruptions: California Division of Mines and Geology,
Geologic Data Map No. 6, map scale 1:750,000.