Geoscience Reference
In-Depth Information
Usually the Bouguer reduction is performed using a constant density
0
;
the density defect ∆
must then be computed by
∆
=
H
D
0
,
(3-68)
which differs slightly from (3-50), in order to restore equality of mass ac-
cording to
(
0
−
∆
)
D
+
0
H
=
0
D.
(3-69)
The first term on the left-hand side represents the mass of the layer between
the level of compensation and sea level; the second term represents the mass
of the topography, now assumed to have a density
0
.
Airy-Heiskanen system
Again we use
A
C
=
∆
A,
(3-70)
where
b
and
c
in (3-22) are, according to Fig. 3.12, given by
b
=
t,
c
=
H
P
+
T
+
t,
(3-71)
0
=0
.
6 g/cm
3
.
and
is replaced by ∆
=
1
−
P
H
H
P
P
0
T
HTt
P
++
Tt
+
t
root
Fig. 3.12. Topography and compensation - Airy-Heiskanen model
Total reduction
In analogy with (3-38), the topographic-isostatically reduced gravity on the
geoid becomes
g
TI
=
g
−
A
T
+
A
C
+
F,
(3-72)
