Early studies focused on fault zone thickness including fault damage zone and fault rock (gouge). For example, Knott et al. (1996) presented data including fault zone thickness in various lithologies. Evans (1990) questioned a universal thickness-fault displacement or slip relationship and warned that conceptual and quantitative models which rely heavily on thickness-displacement relationships should be considered with caution until further data are collected on the topic. Although much more data are available since 1990, the subject is far from settled.

We focus here mainly on two thickness parameters for faults: the thickness of fault core or fault rock and the thickness of the fault damage zone. These are addressed separately for faults formed by particular mechanisms under the links below.