7. OVERALL CONCLUSIONS
The study of strong earthquakes is not the same, as it
could be, when studying other physical phenomena. Actually, if a
seismological experiment is conducted in real time, it is not
guaranteed that within the time span of the experiment some strong
earthquakes will take place, serving thus the purpose of this
research. On the other hand, it is completely different to fracture
rock specimens, under laboratory conditions, from studying an
earthquake under natural conditions. The character of the rare
occurrence of strong earthquakes poses a real problem to the study
of their prediction.
As a first approach, the chaotic, in time, behavior of their
occurrence led the researchers to apply statistical methods. Some
"return times" of occurrence, at specific, seismogenic areas, were
found through the used, statistical methodologies. This was
especially facilitated, where long seismic history was recorded in
the past, thus enabling statistical methods to be applied.
Consequently, seismological research, aiming into earthquake
prediction, developed with, mainly, statistical methods (and use of
earthquake catalogs) in countries with low seismicity, while in
other highly seismogenic countries the earthquake prediction topic
was additionally dealt with other methodologies, too.
An important parameter, generally, in any “in situ" earthquake
prediction research project, is the country, where this project will
be performed. It is evident, that not all countries are suitable for
such research activities. What is actually required is a high, seismicity country, which will provide in a reasonable time span (as
long as the research project lasts) the adequate, seismic events, so
that any postulated theoretical scheme can be successfully tested.
Greece, a country with large seismicity, due to its location on a
major, seismic belt, is the country where this research took place.
This facilitated, a lot, the development of the methodology, already
presented, by providing strong enough, seismic events data in a
rather short period of time.
In the course of the development of the earthquake prediction
methodology, the basic principles, as in any research field, were
followed. In brief, these are as follows:
- Observations of some physical parameters are made in
- A theoretical model is postulated, which justifies
the generation of the observations.
- Following the theoretical model, theoretical
observations are made.
- Comparison is made between the theoretical and the
real observations in nature.
In case, a satisfactory agreement is found between the theoretical
observations and the real ones, then the model is adopted as a valid
one that represents what actually happens in nature, regarding this
physical phenomenon. In a different case, the postulated model is
disregarded and a new one is being searched.
A problem the seismologists, who study the topic of earthquake
prediction, face is that there is no physical model mechanism that
accounts for the generation of the earthquakes. Consequently, there
is no way to analyze the problem, in physical, mathematical terms,
and hence, to devise a corresponding earthquake, prediction scheme.
On the other hand, the earthquake prediction problem is referred as
a multidisciplinary one, quite often. Actually, what is suggested by
the term "multidisciplinary" is that geologists propose geological
methods to be involved, geochemists suggest geochemistry,
engineering geologists suggest rock mechanics, geophysicists suggest
geophysical methods and so on.
In the course of the presentation of the methodology for earthquake
prediction based on electrical signals, recorded, on ground surface,
three different physical models were postulated. The first one is
the oscillating, lithospheric plate, due to Moon - Sun interaction,
which generates the tidal waves. The second one is the homogeneous
ground Earth. This facilitates the epicentral area determination.
The third one is the lithospheric, seismic energy flow model, which
facilitates the magnitude calculation. Instead of one physical
model, required, as a prerequisite, three different models were
combined in order to provide an acceptable solution for all
predictive earthquake parameters (time, location, magnitude).
Consequently, the term "multidisciplinary" is defined now, in the
field of Physics, as stress-strain maxima of a seismogenic area, due
to lithospheric oscillation, seismic energy release through an "open lithospheric physical system" and homogeneous, electrical properties
of Earth, due to long wavelengths of the used electrical signals.
The corresponding theory, which was used for each model, was
presented, following basic principles of Physics and Geophysical
theories. Each model was tested against actual observations that
comply with the theoretical ones. Therefore, the postulated models
represent, to a very large degree, the seismological reality of an
under study seismogenic region.
Largely innovative ideas were introduced, in order to overcome the
various difficulties that were met in the course towards earthquake
prediction. The most severe problem, met, is the noise contamination
of the preseismic signals. This was treated with the newly,
introduced, "noise injection" technique.
Moreover, the presence of various, different, electrical
signal-generating mechanisms in the focal area was treated by the
adoption of the "apparent point current source". The term "apparent"
is quite often used in Applied Geophysical methods. Finally, the
energy conservation law of Physics was introduced for the analytical
calculation of the magnitude of a future earthquake.
The three prognostic (location, time, magnitude) parameters of a
future strong earthquake were calculated analytically, using the
latter three physical models. Following the basic principle of
scientific research, these methodologies were validated by real
strong earthquake data. Consequently, the proposed methodology that
complies with the seismological observations made by seismological
methods is a valid one. In contrast to statistical methodologies, it
is a, more or less, deterministic methodology, which is
characterized as "short-term prediction" or even more as “immediate
prediction”, since the time window which is achieved by this
methodology, is of the order of hours - days.
As a by-product of the method which is followed for the
determination of the “magnitude” parameter of an earthquake, are the
compiled "Seismic, Potential Maps". These maps can be considered as
prognostic tools for an intermediate-term prediction.
T he obvious question is: are all strong earthquakes
predictable? The answer is no!! Actually, predictable are the
earthquakes that are capable to generate electrical signals and
consequently, the presented methodology can be applied to. These
earthquakes are the ones, which occur in the crystalline part
(crust) of the lithosphere. The main idea is that, preseismic
electrical signals are generated, due to crystalline deformation, by
any valid strain inducing physical mechanism. The earthquakes,
located, in the part of the Earth’s outer-shell, where plasticity
exists (upper mantle, lower lithosphere), are not capable to produce preseismic, electrical signals. Therefore, in this case this
methodology cannot be used.
It is anticipated that, this methodology can be improved further
more. A topic that should be studied in detail is the application of
a weighting factor in the calculated azimuths, according to the used
signal amplitude. In the present methodology, the real azimuthal
direction is determined as the average value of all individual
azimuths, calculated from all data points, regardless of the
corresponding signal amplitude. Instead, a threshold was selected,
so that the preseismic signal would be kept above a certain level
from ambient noise.
Another topic that is very interesting and should be addressed to
is the preseismic signals azimuthal directions, in relation to the
regional - local stress field, observed, at each seismogenic area.
As far as it concerns the practical application of the methodology,
a wide, monitoring network is required, in order to cover, in an
even density, a largely, extended, seismogenic country.
In the particular case of the Balkan Peninsula which presents high seismicity, is required a network which will cover up the
neighboring countries of Greece (Albania, FYROM, Bulgaria, and
Finally, it must be understood that this presentation does not
exclude the existence (in the future) of any other methodologies,
with even better accuracy than the one, which has been achieved with
the present work. I hope that some other eager and younger
researcher will either improve it or invent a better one, in the
What is only required, is to believe that a problem shouldn’t be
considered unsolvable, just because it was not solved for a long
period of time, in the past.