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Image
FESN
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The
earthquakes of Gaia are one of its more terrible manifestations,
but also mark the obvious signs of its intrinsic life.
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Image from:
I regni della Vita
La Terra – Mondadori
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Perhaps
the ancient fear of the man towards this terrible manifestation
derives from the fact he has always considered the earth like
something solid, immutable, sure, often identifying the earth
as his own house.
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As
evidence of this theory it is enough to think about the long
travel of Columbus, after having crossed the ocean, he came
down to kiss the ground of the island, that he baptized as
Saint Salvador.
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The
earth is a result of various chemical-physical elememts, more
precisely 92,as listed in the "Table of Elements" in opposite
the four fundamental elements: Earth Water Wind and Fire;
these regard the ancient alchemistic discipline.
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Nebula
Dumb Bell in Vulpecula
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Every
one of the 92 elements that constitute the ingredients of
the universe are formed from primitive hydrogen and from the
activity of the "stellar workshops". Same as us , we are the
fruit of the extinct star activity.
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Anciently
the shaking of the earth was believed to be the work of Titaniums,
that within enormous workshops hidden in the middle of the
earth, they fused weapons for the Gods.
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Image from
: I regni della Vita
La Terra – Mondadori
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The
Fenicies believed in the middle of the earth, there were other
skies, lands and oceans. And other suns with sunrises and
sunsets in small universes with the same center.
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Image from
: Modello Sismotettonico dell'Italia Nord Orientale – Consiglio
Nazionale delle Ricerche
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Recently
geologists believed earthquakes were the result of great underground
landslides relating maybe to meteorological phenomena, like
intense rains and drought. Another hypothesis, suggested volcanic
activity, but this is contradicted with the evidence with
Friuli, the obvious lack of volcanoes also extinguished, in
this region.
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Image
from : Il grande libro
della Preistoria - Vallardi
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During
the sixties, the acceptance from part of the scientific community
of the "Theory of the sods" that assumed the existence of
two great continents, with their joining they constituted
the "Pangea", and then subsequently fractured in to other
smaller continents, also changed the attitude of the scientists
towards earthquakes.
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Image from
author
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The
clues on the surface supporting the theory, were the similar
flora and the fauna in zones that currently exist on distant
continents.
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Image
from : La tettonica delle
placche - Zanichelli
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The
awareness of the "Theory of sods" and the "Continental Drift"
is revealed also from the study of oceanic bottoms with military
purpose during WWII , when appropriate surveys have put in
evidence the young age of the bottoms compared with the continents.
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Image
from: Quark – Hachette Rusconi
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World-wide
seismic mappings therefore have put in evidence the existence
of fracture lines, and the generation of new oceanic bottoms,
with other lowering zones under continental plates.
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Image
from : I regni della Vita – Le montagne – Mondadori
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Along
the production lines of new crust, are produced some grooves
so named "rifts", wich are the parents of the new oceans.
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Image
from : La tettonica delle
placche - Zanichelli
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In
proximity of the crash between continental plates, mountain
chains are produced, whose height is different according to
their age. Atmospheric agents in fact erode the elevation of
the cliff layers until to reduce them completely. Without their
action the Alps would be higher by 25.000 meters or more. |
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On
the other hand without the constant action of production due
to the production of new land crust, in 65 million years every
hill or mountain would definitively reduced to sand, modifying
in this way the habitat of the planet. |
Image from:
Quark – Hachette Rusconi |
The
heat inside of the planet, approximately 6000° in the nucleus,
evidenced from volcanic activity, shows the existence of fluid
rocky material, over which the continents are moving. |
Image
from author
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The inner
heat of the planet, seems to be a result of the residual cooling
of the planet, entirely constituted from fused rocks, and partially
from the decay of the natural radioactivity. Along the zones
of "subduction", where the crust is pushed under the continental
plates, moreover, intense heat, that is caused from the tremendous
frictions between the cliffs, occurs. |
Image from
: I regni della Vita – Le montagne – Mondadori |
The
study of these seismic clues therefore has added to the elaboration
of new theories that have aided in developing a map of the inner
part of the planet and to assume the mechanisms that produce
the terrestrial magnetism. |
Image FESN |
The
seismic traces in fact contains information of approximately
the density and the thickness of the inner layers of the planet,
that it stacks one over the other like in an onion. The information
is taken out from some particular activities of the seismic
waves, whose variability depends just on the crossing of borders
between layers of various density, and on the ability to cross
fluid layers. |
Image from:
USGS |
Along
the seismically active zones, faults are formed, and are called
"normal, inverse or transform" depending on the type of movement
of cliff layers involved at the phenomenon. |
Image
from: USGS
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The
seismic events are characterized with an "epicentre" where the
seismic waves get started and run along the surface, and the
"ipocentre", effective source, in depth, of the forces causing
the movements of the rocky layers and of the seismic waves that
they generate. |
Image from:
I terremoti - Zanichelli |
The
different characteristics of types of waves that occur during
the seismic events, allow us to reconstruct either ipocentre
or epicentre, comparing the times of arrival of the various
waves to the several stations that constitute one seismic net. |
Image
FESN
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The
seismic waves can be subdivided in to two main types: the waves
"P", faster; and the waves "S", a little bit slower. The difference
of arrival to a station allows us to know the distance from
the station of the epicentre. On the other hand, the times of
arrival of the waves "P" to the stations, allow us to know the
ipocentre point. |
Image from: CRS |
Having
on hand the minimal number of three stations, opportunely situated,
makes it therefore possible to calculate the main characteristics
of the seismic event, which intensifies in class of Magnitude,
epicentre and ipocentre. |
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The
value of power of the seismic tremor, once based on the Mercalli
scale; constructed estimating the manifestations in surface,
nowadays, thanks to the instruments named "sensors" based on
precise appraisals and calibrations, allow us to know the effective
intensity of the forces unchained at the ipocentre. The scale
of effective power of the events is called, in honour of its
inventor "Richter Scale". |
Satellite image |
The
particular formation of Italy is therefore a result from the
push that the African continent carries out towards Europe.
The volcanoes existing in Sicily indicate subduction zone in
the crust, the Apennines indicate a push that will join, in
a far away future, Italy to the former Yugoslavia, while present
the alpine chain is the result of a further subduction. The
part of the crust on which lays Italy, moves and is pushed under
Europe in proximity of the line named "Insubrica" situated along
the Austrian valleys, north of the Alps. |
Image FESN |
The
situation of the Friuli is rather complex, because right in
this zone is situated the fulcrum of the movement of the Italian
peninsula. The vicinity of the subduction zone and the complexity
of the fractures, and the faults, keep this zone particularly
subjected to seismic phenomenon, so it is hard to forecast. |
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The
presence in Friuli of numerous seismic stations, managed from
the main national institutes of research, but also the presence
of instrumentations able to measure the superficial movements
of the crust, and the effective heights of the reliefs, today
allows us to estimate which forces are effectively in action,
while they interact in order to provoke earthquakes of tomorrow. |
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The
everybody's hope is, in the future, to discover the imperceptible
marks that indicate the imminent arrival of a destructive tremor,
allowing us to act in time. The historical seismicity, in fact,
induces us to think that in Friuli the time of return of a meaningful
event is approximately 50 years. |
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We
wish all the scientists to be in time. About us, our attempt
is to introduce in the best way possible this interesting
matter, as we are sure that the spread of the information
is one of the possible methods of prevention.
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