Abstract - Measured populations of fault displacements,
derived from regional seismic, oilfield seismic, coalmine plans and outcrop
data show a power law distribution with exponents (-S) of -0.45 to 0.95
for single-line samples across an array of faults. An expression for a
population of active faults, derived from the Gutenburg-Richter magnitude-frequency
relation for earthquakes is log N = a - bD log D, where D =maximum
displacement of a fault, N=number of faults of maximum displacement D or
greater and bD = ca 1.0 and has the same value as b for the
corresponding earthquake population. Populations of 'dead' faults existing
at the end of a tectonic episode have been numerically derived, using a
fault growth model, and satisfy the relation log N = a - E log D, where
E has a value between 1.6 and 2.0. Numerically derived populations of fault
displacements in a dead fault population have slopes of -S where S = ca
E - 1. The contribution of an individual fault to the regional strain varies
with the lifetime seismic moment of the fault and is proportional to D2.
Estimation of fault-related extension by summing heaves on faults of a
limited size range is valid only if the measured size range of fault accommodates
most of the extension. Correction can be made if the S value of the fault
displacement is known.
Journal of Structural Geology 14, 701-712, 1992.