Trudy GAISH, vol. LXV, 1996
Abstracts
The global distribution
of average (5Ox5O)
depths
of Mohorovicic discontinuity
on the Earth
by P.A.Stroev, E.D.Koryakin, A.N.Groushinsky
The available seismic data for the thickness of the earth
crust were compiled and averaged on the 5Ox 5O grid
for the whole Earth. For any distant and inaccessible, and by this reason
poorly known, regions, such as high mountains of the Middle, South and
Little Asia, American Cordilleras and Andes, Antarctica, Greenland and
so on, these data are absent. So, for such regions the depths of Moho discontinuity
was estimated by means of the correlation between the thickness of the
crust, topography and Bouguer anomalies. For each cell of the grid the
depth of Moho discontinuity was determined by averaging of all data, existing
in this cell. In the cartography grid of the Earth, there are 2592 cells.
The cells, which contain data for the thickness of the earth crust, cover
approximately 80% of the Earth surface. The summary of these cells is presented.
The resulting map of the Moho discontinuity depths with the isoline interval
equal to 5 km is drawing. The reliability of the resulting data was estimated.
A Spherical Harmonic and
Statistical Analysis
of the Moho Surface (M)
Depths
by N.A. Chujkova, T.G.Maximova
The Moho surface (M) depths are expanded in terms of
a spherical function system up to the degree N = 30. The statistical
analysis of the expansion carries on to the following principal conclusions:
1) The average M depth is 22.37± 0.20 km.
2) The displacement of the M figure center from
the Earth center is 9.31 km in the direction: the latitude = -39.9 degrees,
the longitude = 230.9 degrees.
3) The polar M flattening is 0.0053, the equatorial
one is 0.0015. They considerably exceed the geoid flattenings (0.00335
and 0.00001).
4) The principal features of M relief are represented
in the 9 degree expancion.
The maps of the M depths (relative to geoid) and
of the M altitudes (relative to the hydrostatic figure) are obtained
and analysed for N = 30,9,5. The reliability of the resulting data
is estimated.
The Spherical Harmonic and
Statistical Analysis of the
Earth Equivalent Rock and
its Isostatic Compensation
by N.A.Chujkova, A.N.Grushinsky, T.G.Maximova
The equivalent rock topography r is represented as
the spherical function expansion up to degree 30. That expansion is compared
to the Moho surface expansion and to the gravity field of the Earth. The
principal results are:
1) the mean radius of r is 6369.62 km;
2) the r figure center is displaced from the Earth
center at the distance of 1.04 km in the direction 
;
3) the polar r flattening is 0.00329, the equatorial
one is 0.00017;
4) isostatic compensation of topography exists on the
depths less then M depths for degree more or equal 3, and deeper
for degree equal 1 and 2;
5) the difference between the geoid flattenings and the
r and hydrostatic flattenings is caused by the large M flattenings;
6) the estimation of the Moho depths by means of the correlation
with the Bouguer anomalies are not confirmed. The estimation on the basis
of the isostatic compensation hypothesis is possible only for large-scale
Moho extension, which are characterized by the expansion of 10 degree and
less.
The search of sources of
the gravity anomalies
by S.A.Kazaryan
The interpretation of sources of the anomalies of the
Earth's gravity field is carried out. The point sources were placed under
the largest geoid's anomalies. Their coordinates, masses and limit depths
of the location are determined. Such analysis allows detecting whether
the sources of the largest anomalies reside within the Earth's core. This
is possible if the limit depths of the sources exceed the depths of the
core-mantle boundary.
The Earth core's internal
structure as a total source of gravity and magnetic fields anomalies: preliminary
results
by N.A.Chujkova, N.V.Alakverdova
The problem of the search of the correlative dependence
between the gravity and magnetic anomalies is investigated. This dependence
should exist if gravity and magnetic fields have common sources of the
different shape and origin, laying in the outer core.
The formulas of gravity and magnetic potentials of such
sources are received. The original method of search of correlative dependence
for the sources, laying in the common axis is worked out. The method is
tested using the concrete models of Earth gravity and magnetic fields,
base on the observations.
On the Earth's Inner Core
Dynamics
by Yu.V.Barkin
The differential equations of the inner core motion in
liquid core of the Earth under attraction of the mantle and Moon and Sun
have been obtained. These equations were reduced to the equations with
conditionally-periodic coefficients. The frequencies of the inner core
librations and phenomenon of the constant displacement of the center mass
of the rigid core are investigated. Secular and periodic perturbations
in the inner core motion due to main geophysical processes have been studied.
On the polar free oscilation
of the Earth’s Inner Core
by Pasinok S.L.
Influence of the Earth’s cover on the polar free oscillation
of the Earth’s inner core is considered. Two cases of the Earth’s cover
were studied , corresponding frequencies are calculated.
Dependence of the reversals
frequency of geomagnetic field
on the position of Solar
system in the Galaxy
by N.A. Chujkova, K.V. Semenkov
The problem of the Sun’s motion in the Galaxy is solved,
the Sun’s orbit for a modern model of Galaxy potential is calculated. Fourier-analysis
of time dependence of geomagnetic reversals frequency for 550 million years
is made. Next regularities are revealed by comparing palaeomagnetical data
with Sun’s position in the Galaxy: the frequency of geomagnetic reversals
is a maximum when the Sun’s system cross such Galaxy’ regions where the
gravity potential and ambient physical characteristics are varied to the
utmost, namely, when the Sun leaves the Galaxy’ spiral arms, the Sun cuts
across the Galaxy disk, the Sun is at the minimal distance from the Galaxy
centre.
To specify received regularities and to find out their
causes further investigations are needed.
The mass and the moment
of inertia of the Earth
by V.E.Zharov
There are the discrepancies between the observed and
theoretical amplitudes of the nutation terms. One of possible explanations
of this is the application of the simplified model of the Earth consisting
from the elastic mantle, liquid outer core and elastic inner core. More
complex model have to be considered. One of more complex model of the Earth
has been proposed by Chujkova and Maksimova [1]. The main conclusion is
that the Mohorovichich surface's ellipticity is greater than that of the
crust and the center of ellipsoid has bias from the center of Earth's mass.
The estimation of the mass and the moment of inertia of the Earth with
new model of Moho surface and biased inner core has shown that our result
is consistent with the common values. So this model can be used for further
investigation.