Page 272 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

z,,),
255
x:
and
to
respect
[x/z,])}
Modeling
(z,
dx
slabs
[x/z,,])
with
tan™
rap}
the
Gravity
of Ag,.
tan7!
of
+
x
tan7'[x/z,])
=
(@/2
depths
tan™![x/z,])
-
dx
tan™
integral
[x/2,]
[x/2_])
—
the
tan~'[x/z,])
+
pA(Ah)

= Am/A
(Ap)A(Ah)
—[Am],,
0
é
({Am),/A)(a/2
of
the
(tan7"
slab.
=
+
tan™!
slab
regardless
{([Am),/A)(a/2
—
dx
is
(Ap)(Ah)
mantle
(tan7'[x/z,]
=
curve
Ag
water
=
—
2G({Am],/A) |
[Am],
=
+a
that:
(tan™"[x/z,]
+
Am
anomaly
{(a/2
of the
zero:
that,
the

implies
+
of
show
is
2G({Am],/A)
2G({Am],/A)
|
excess
deficit
+&
air
2G
x
equilibrium
—m
tables
free
to
=
=
mass
mass
—%
Ag,
dx
the
Ag,
integral
from
ul
under
=
=
[Am],
[Am],
slab:
isostatic
Ag,
integral
therefore:
therefore:
Standard
area
each
that:
that:
where:
Airy
The
.
the
For
so
so
air free the for curve the under area the that demonstrates expression last The models the of each in seen is relationship This 8.34a). (Fig. zero equals anomaly equilibrium. isostatic local of state a in are that below density a and profile, anomaly gravity air free observed an
Near Zero, 0 = mass zero integral Bouguer correction a passive
Values Curve Under = Negative Area #Am!= Am) in local isostatic equilibrium. of deficient 0. The = Bouguer anomaly al
_| Free Air Anomaly with Area (Positive Area because 150 toe 1 margin the absolute value equals ({Ag, dx) to x respect to zero. b) The air anomaly curve sum form of the general slab). each for (same
Free Alr Anomaly -Am Ocean Gi) for passive conti mass (1+ Am!) of excess gravity with in free (a). yields the slab of a =m/V A(Ah).
Isostasy = 2.67) Ocean Boundary lies of the change areas under the area =
and 1.03) (p, 3.1) 0 (km) X \ Mantle (p,* 3.1) 1 t gravity means the absolute value air anomaly in surface is: slab slab of a
Gravity Negative Area Water (p,= Mantie Bouguer Corrected Water (p en) Contant Bouguer integral negative free to the horizontal slab of a of a mass volume
Chapter8 Positive Area omen mover Crust (p,~ 2.67) Continent Cnust (p," 2.67) Distaticw Free air and this equality, the positive and (Fig. 8.9b). applied margin. = A density m Ul V =
a 8.34 Isostatic equilibrium Let: The where:
4 J -150
254 Ss § FIGURE (!-Aml). With means that the sea continental
(eDwW) Aewouy Ayawsp a) at