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At present the Earth is a complex multilayer body. Each of the layer has a rather complicated
structure, which studied by various geophysical methods (seismic, magnetic, gravity, and others).
The study was initiated by K.E. Bullen, Australian seismologist who in early 40-ies proposed to
divide Earth into zones identifying relevant by letters: A - the crust of the total thickness 35km and a
density of 3.2 g/cm3, B – in the layer deep between 33-413 km and a density of 3.5 g/cm3, C - zone 413-
984 km and a density of 4.0 g/cm3, D - zone 984-2898 km and a density of 5.0 g/cm3, D - 2898-4982 km,
F - 4982-km, G - 5121-6371km (center). These zones differ by seismic characteristics. The last zone D was
subdivided by zones D' (984-2700km) and D" (2700-2900 km). By nowadays the scheme was significantly
modified and the only layer D" is widely used in literature. Its main feature is in decrease of gradients of
velocities seismicity compared with the upper layer of
the mantel. Outer core (E) of density 10-11g/cm3
Density range Volume
percentage percentage %
reaches the depth of 4980km followed by transition
crust A 33km 2,7 - 3,0
zone till 5120km. Inner core is located at depth of
3,32 - 3,65
6371km od 12g/cm3 density.
3,65 - 4,68
Fig.8 shows the internal constitution of the Earth
4,68 - 5,69
by G.B. Voitkevich, as modified and amended.
Zones B and C form the as so called upper
9,40 - 11,5
mantle, and zone D lower mantle. The Earth mantle is
formed by silicate rocks. With increasing pressure and
F 5100km 11,5 - 12,0
temperature phase transitions occur in the material:
12,0 - 13,0
certain types of rocks from the solid transfer to liquid.
Such transitions observed in zones C and D'. In the
latter the entire metal is molten and the outer core
(zone E) entirely consists of molten metal. Transverse
waves do not pass through this zone because shearing module is equal to zero. In the transition zone F
liquid metal transfers to solid phase and inner core is formed by solid metal with a density of 12. However,
there is an assumption that if to change physical conditions and keep this metal under normal temperature
and pressure condition its density will be equal to 7. Herewith, inner core surrounded by molten metal
cannot remain solid as should melt.
The Kola superdeep well SD-3 allowed to study subsurface and understand the behavior of rocks at
high pressures and temperatures. The idea that rocks with the depth become thicker and their porosity
decreases was incorrect same as the point of view existing on the dry subsoil. For the first time it was
discovered during the drilling of the Kola superdeep well. Other wells in the ancient crystal rocks
confirmed that in many kilometers down rocks are broken by cracks and penetrated by numerous pores
and water solutions freely move under pressure of several hundred atmospheres.
The fact that the continents are composed of very ancient rocks, ranging in age from 1.5 to 3 billion
years is not denied even by Kola superdeep well. However geological cross-section of the kern sampled
from SDW-3 shows exactly opposite evidence that scientists had previously considered. The first 7
kilometers were represented by volcanic and sedimentary rocks (tuffs, basalts, ruttles, sandstones,
dolomites.)In the deeper layers there was found so-called Conrad section after which the speed of seismic
waves in rocks sharply increased which was interpreted as boundary between granites and basalts. This
section had been passed but basalts of the lower layer of the Earth crust never appeared. On the contrary
granites and gneisses found.
Cross-sectioning of the Kola well denied a two-layer model of the Earth crust and showed that
seismic sections in the subsoil are not discontinuation of rocks of different composition. It is likely
indicates that stone get different properties with depth. It is probably that at high pressure and temperature
properties of rocks can strongly vary as granites’ physical characteristics become similar to basalts and in
reverse. But basalt taken to surface from 12-km depth immediately converted to granite although sensed
along its way the strongest attack of “decompression illness” – kern crushed and broken by flat disks. The
deeper was the well the less quality pieces were sampled by scientists.
There were lots of unexpected in the depth. Previously it was common to think that than deeper the
pressure is higher and rocks more solid having smaller number of cracks and pores. SDW- 3 has assured
scientists in reverse. At 9 kilometers depth the layers were found excessively porous and fed with cracks
through which water circulated. Later this fact was confirmed by other ultra-deep wells drilled within the
continents. The temperature of the deep layers appeared much higher than expected: by 80°. At 7km the
temperature at the cut face was 120°C and at 12 km reached 230°C.
4.2. Existing Models of Earthquakes Mechanism
Quite satisfactorily explanation of the causes and sources of origin of most earthquakes is given in
the framework of plates’ tectonics theory. Its main idea is that in the marginal edge of each plate at the
adjusted boards rocks appear under the strong influence of deforming (tectonic) forces arising in them
physical and even chemical alterations. Exactly the edges of the geological structures are exposed to
greatest influence of forces produced by the movement and collision of the plates where major geological
conversion occurs. 
Earthquakes mechanism is very complicated process and seismologists are only at the beginning of
its understating. Strong earthquakes are caused by a sudden shearing of certain rocks along relatively large
plane of the fault; therefore mechanism of earthquake represents the kinematics expressed by motion
within the source. There are a few most common models of earthquakes sources mechanism.
The earliest model developed by H. Reid, 1911 based on elastic drift during shearing deformation of
rocks, where break point is over exceeded. Model by N.V. Shebalin (1984) suggests that the main role in
the occurrence of short-term waves with large accelerations play nuisances, roughness or “hooks” along
the main fault where the shearing occurs. “Hooks” restrict free shifting or creeping and they do accumulate
tensions within the source. Model developed by V.I. Maychkin in Russia on avalanche-unstable fracturing
based on rapid build-up of cracks. During such interaction and formation of main or major fault with
shearing of rocks accumulated tension rapidly releases creating elastic waves. Another model developed by
U. Brace and A. M. Noor, American geophysicists in late 60-ies suggests that dilatancy, i.e. increase in rock
size during deformation, plays the main role. Microcracks being filled with water are not able to close in
return. Thus the rock increases in size thus enhancing tension. At the same time pore pressure is growing
and robustness of the rock is decreased. All this build-up tension i.e. earthquake.
There is a model of unstable creeping that is most completely developed by K. Scholz, American
geophysicist in 1990. The main idea is “sticking” of cross-moving blocks while the surface of the “creeper”
is relatively smooth. Sticking leads to the accumulation of shearing tensions while releasing convert into
Geophysical observations prove the plates’ tectonics theory indicating continues rise of magna within
mid-oceanic ridges. Getting cool it transforms to new seabed and moves in spreads directions from the
ridge. Thus plates expand and move with the same speed getting more cool and old getting further from
the ridges. Shears are transformed caused lots of earthquakes along both of the edges.
Plates move irregularly and rest for a long time pressing on other’s edges. But gradually convection flows beneath them
increase the pressure so plates rapidly displaced. It shakes all adjacent rocks causing earthquake – stated Gutenberg B.
and Richter C. in paper Elementary seismology.
4.3. Features and Characteristics of Earthquakes to be Studied
According to the plates tectonics theory indicates more earthquakes should have to occur on the
edges of interacting plates (so-called interplate earthquakes) than from the inner parts of the plates.
However in the inner parts of the plates earthquakes are more frequent and the plate tectonics theory does
not give any logical explanation to this fact.
Stable growth rate of plates gives grounds to assume that on the edges of the plates the creeping pace
should remain constant. Therefore it should be expected as a logical process that next earthquake shall
happened close to the occurred. However, in contrary to logic, on the edges of the plates is often seen a
zone of seismic silence that also cannot be explained by this theory.
The hypocenter or source of the earthquake is taken as some point (a spot of a small area) where at
the deep layers earthquake occurs. Exactly such data are read from seismicity reports: geographic
coordinates (latitude and longitude), depth, and magnitude (energy class). If earthquake would be caused by
collision of plates its hypocenters would from an extended structure or line in plane and a slab in
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