Geology Reference
In-Depth Information
Fig. 6.6.
Vertical and horizontal exag-
geration. A bed of original
thickness
t
is shown in
white
.
a
Unexaggerated cross section.
b
Horizontally exaggerated
(squeezed) cross section.
c
Vertically exaggerated cross
section
and is common, along with vertical exaggeration, in the presentation of seismic lines
(Stone 1991). Reducing the horizontal scale (squeezing) makes a wide, low amplitude
structure more visible and makes the break in horizon continuity at faults more obvi-
ous. Squeezing exaggerates the structure without producing an unmanageably tall cross
section.
Vertical exaggeration (
V
e
) is equal to the length of one unit on the vertical scale
divided by the length of one unit on the map, and horizontal exaggeration (
H
e
) is the
length of one unit on the horizontal scale divided by the length of one unit on the map
(Fig. 6.6):
V
e
=
v
v
/
v
,
(6.1)
H
e
=
h
h
/
h
,
(6.2)
where
v
v
= exaggerated vertical dimension,
v
= vertical dimension at map scale,
h
h
= exaggerated horizontal dimension, and
h
= horizontal dimension at map scale.
As derived at the end of the chapter (Eqs. 6.21 and 6.22), the true dip is related to the
exaggerated dip by
tan
δ
v
=
V
e
tan
,
(6.3)
δ
tan
δ
h
=tan
δ
/
H
e
,
(6.4)
where
=true
dip. Equation 6.3 is plotted in Fig. 6.7. In its effect on the dip, a vertical exaggeration
is equivalent to the reciprocal of a horizontal exaggeration (from Eq. 6.24 at the end of
the chapter):
δ
v
= vertically exaggerated dip,
δ
h
= horizontally exaggerated dip, and
δ
V
e
=1/
H
e
.
(6.5)
