Geology Reference
In-Depth Information
Table 7.1. Ratio of maximum displacement to length for a variety of faults that die out in tip lines in the
direction of the measurement. The first two measurements from Rippon (1985) are from Fig. 7.24a, the
third is from Fig. 7.24b
mum displacement and so the displacement/length ratios could be smaller than the
values recorded in Table 7.1. The examples of Rippon (1985), however, are well ex-
posed in three dimensions and the ratios are very large. In summary, long faults usually
have large displacements but may have small displacements; short faults do not have
large displacements.
The relationship between the maximum displacement and the fault length is gen-
erally considered to have the form
L C ,
D =
γ
(7.9)
where D = maximum displacement,
= a constant of proportionality, L = fault length,
and C is between 1 and 2 (Watterson 1986; Marrett and Allmendinger 1991; Dawers
et al. 1993). The exact relationship appears to depend on many factors including
the mechanical stratigraphy and the nature of interactions between overlapping
faults (for example, Cowie and Scholz 1992). For the practical estimation of the
displacement-length relationship in map interpretation, it appears satisfactory to let
C = 1 and recognize that the value of
γ
may change when the size of the fault changes
by an order of magnitude and will be different in different locations (Cowie and Scholz
1992; Dawers et al. 1993; Schlische et al. 1996). With C = 1, the value of
γ
is the
D / L ratio given in Table 7.1. This relationship can be used to estimate the length
of a fault from its maximum displacement or estimate the maximum displacement
from the length.
γ
 
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