Geology Reference
In-Depth Information
7.4.1
Slip
Slip (or net slip) is the relative displacement of formerly adjacent points on opposite
sides of the fault, measured along the fault surface (Bates and Jackson 1987). Slip is
commonly described in terms of its components in the plane of the fault, dip slip and
strike slip (Fig. 7.16a). Dip slip components are normal or reverse and strike slip com-
ponents are right lateral or left lateral. The offset of a marker horizon, as recorded on
a map, can be produced by slip in a variety of directions. The geometry of the fault and
the offset horizon are identical in Figs. 7.16a,b but the fault in 7.16a is oblique slip and
in 7.16b is pure dip slip.
There are two traditional approaches for finding the net slip on a fault. The most
direct is to find the offset of a geological line that can be correlated across the fault. A
geological line may be a geographic or a paleogeographic feature such as a stream
channel or a facies boundary. The alternative is based on the distance in the slip direc-
tion between correlative planar surfaces. In this method the slip direction must be
known, for example, from the slickenline direction. The orientation of the slip vector
may be recorded as the bearing and plunge of the lineation, or as the rake, which is the
angle from horizontal in the plane of the fault.
Fig. 7.16.
Displacement of a marker
horizon (
shaded
, w ith
dashed
contours
) across a fault (
un-
shaded
, w ith
solid contours
).
The final geometries of
a
and
b
are identical although the
slip is different.
Wide contour
lines
represent correlative lin-
ear features displaced by the
fault.
ds:
dip slip;
ss:
strike slip.
a
Right-lateral, normal oblique
slip.
b
Normal dip slip
