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About seismics

Glikman A.
Scientific firm "GEOPHYSPROGNOS"
Saint-Petersburg

     Anyone investigation method, including, and the geophysical method can be effective only in the event that it is based on quite concrete physical effect. And on the contrary, if the basis of a research method is not observed experimentally this method it will be inevitable to develop in a deadlock direction.
     In other words, potential ability of a geophysical method is in rigid dependence on as far as real properties of a used physical field are taken into account.
     But it was so, that the most important in geophysics the method - seismic prospecting - was created without taking into account real properties of a field of elastic fluctuations in solid materials, and in a basis of this method there was just such, nonexistent effect. Poisson has offered idea echolocation in massif as model of seismic prospecting. He thought, shock generates an elastic (sound) pulse which should be spread in all directions in massif and also be reflected from borders taking place in terrestrial thickness according to laws of geometrical optics.
     In the beginning of XX century, approximately in 70 years after Poisson formalized his idea, experiments with realization of seismic works was begun. However from this time, and down to our days nobody saw echo-signal as well as primary outgoing sound pulse.
     Instead of an expected echo-signal which as presumptive, should have the same kind and the same spectrum, as well as a primary pulse, seismic signal from the very beginning was long, slowly fading oscillatory process of unfairly big amplitude. Long oscillatory process is observed in immediate proximity from a point of shock influence, not allowing to see a primary probing impulse. All this did not correspond to the mathematical description of all processes which, on presentation of scientists, should occur at seismic works.
     In a usual situation when results of experiment do not correspond to an initial hypothesis, it is necessary to find the reasones of this discrepancy. In this case it has not taken place. Furthermore, at the beginning of XX century it was declared, acoustics of solid materials and, a part of it, seismic prospecting as the science, has finished the development as any situation in acoustics can be described by mathematically.
     It was very strange declaration. To declare end of cognition of any area is a nonsense as the knowledge has no the end. And as to acoustics of solid materials here the similar application and in general should be perceived with humour as a minimum. The matter is that in this area of knowledge till now there is no fundamental position which could be proved experimentally.
     The constancy of speed of movement of elastic waves in homogeneous materials, and even presence of those or other types of elastic fluctuations can not be proved Е
     In acoustics of solid materials any sensor of basic parameters of a field of elastic fluctuations is not created till now. And it means, that any of the arguments that are included in the equations, describing a field of elastic fluctuations, cannot be determined experimentally. But the mathematical equation only in that case concernes to physics if its arguments can be determined in experiment. Hence, from the point of view of methodology, using of the mathematical equation for the description of a field of elastic fluctuations, incorrectly. The consequence of these moments is the neither acoustics of solid materials as a whole, nor seismic prospecting - are not in the competence of metrological services.
     And nevertheless Е
     During 1909-1910 years, at the same time, when it was declared end of development of acoustics of solid materials,, has almost simultaneously taken place epoch-making events in destiny of seismic prospecting. Despite absence an echo - signals, and also that the amplifiers did not exist yet, was made a number of the opening which have put seismic prospecting at once on height, inaccessible for any other geophysical methods. By means of seismic prospecting Mohorovichich, Konrad, Golitsin, Gutenberg surfaces and a number others which are taking place on depths from 10 up to 800 (!) km were open. On the basis of these discoveries the really global conclusions were made: about a liquid condition of a nucleus of the Earth, that the earth's crust under continents is thicker, than under the seas Е Similar statements are very convenient: they can not be checked up.
     The origin of long oscillatory process which is observed at seismic prospecting, was perceived as result of an interference between set of reflections from set of borders deposited in terrestrial thickness. Geophysics began to count this oscillatory process a noise which prevents detection of an echo - signal. And the main tendency of development of seismic prospecting became struggle against this noise. Method of struggle - perfection of the equipment, and then, programs of processing.
     To have money to perfection of the equipment, it was necessary to present seismic prospecting as an effective geophysical method. And consequently the second tendency is a creation of system of the falsifications directed on presenting seismic prospecting as an effective geophysical method. For this purpose seismic prospecting apply only then when already there is a geological information. It can be received with the help of prospecting drilling or (and) with the help of various geophysical methods, and in the report disappears, that this information was already known at realization of seismic prospecting.
     Thus, the opening of many deposits which were open with the help of other means, is attributed to seismic prospecting.
     So, all forces were thrown in these two directions, and directly the physics of formation and spreading of elastic fluctuations are away from interest of seismic prospecting. And therefore, probably, nobody paid attention to a spectrum of this long oscillatory process, that is, directly, seismic signal.
     When in 1977 we have carried out research of spectrum of a seismic signal it was found out, that it have image as a damped harmonic motion, and is more often, several damped harmonic motions. It very much an important point because any interference can not result in occurrence of such signal.
     Physicists, as against mathematicians, are not free in their own actions. If the mathematician, describing mental model, can accept any hypotheses concerning this model, physicist is obliged to move forward in dependance of results of already made experiments. Therefore the researcher who is finding out, that reaction to impulse looks like damped harmonic motion, can not conduct the further work differently any more as on the following, quite certain logic:

  1.      Only the oscillatory system can transform an impulse to a fading harmonic process. Hence, the first, that it was necessary to do after detection of a similar sort seismic signal - is to search, what physical objects act as oscillatory systems. This problem(task) was solved rather quickly, in 1977 when it was found out, that parallel-sided objects almost from all solid materials, including geological structures have this properties. Besides it was found out, that a fading harmonic process is spread along this parallel-sided structure-resonator but not a initial pulse.
  2.      If presence of oscillatory system is revealed, the following step, that it was necessary to make was to find conformity between characteristics of geological structures and their properties as oscillatory systems. This problem also was solved in the same 1977 when empirical dependence between thickness h parallel-sides geological structure and own frequency f0 this structure as oscillatory system was found out:
  3. h=k/f0          (1)

         Disclosure of this dependence started the spectral seismic prospecting/1/, that is a method, is allowed to define thickness of geological layers that are in terrestrial thickness, on the basis of a spectrum of seismic signal.

  4.      Further, it was necessary to find out, first, what is factor k, has dimension of speed and why this factor is marvellously constant for all types of rocks the value equal 2500m/s with a deviation from this value, not exceeding 10%. It was very much an important point because all questions connected to kinematic characteristics of a field of elastic fluctuations, are key. According to directories, there are no such speeds of spreading of elastic fluctuations which would have so identical value in various rocks. On the contrary, as it is specified in these directories, even in the same stratum the speed of a sound can change in some times.

     Besides it was very important to understand, due to that there is a transformation of short impulse impact to a harmonic signal. Development of the theory of spectral seismic prospecting was impossible without understanding of physics of this phenomenon. It was possible to answer all these questions approximately in 1982 when already there was an application of the first generation of the equipment of spectral seismic prospecting. It was the coal mine equipment for forecasting stability of rock of a roof "Resonance". Essential role that we could answer these questions, has played found out then effect of acoustic resonant absorption (ARA).
     In physics it is not much effects of resonant absorption - ferromagnetic, paramagnetic, electronic, gamma-resonance Е Now to these already known fundamental effects it is possible to add and acoustic resonant absorption effect.
     I would like to remind, that the physics is first of all, is sum of physical effects and the phenomena, and each of them is equally important for development of physics. Each of them has value for process of knowledge irrespective of as far as it is appeared understandable at its detection. As known, many of known physical effects for today are perceived on only phenomenological level, however it does not prevent to use them. Resonant absorptions take a special place among physical effects because by their help there is a understanding of other effects and the phenomena.
     Because effect ARA was found out, it was possible to find out sense of factor k in the formula (1) which is a speed of shear waves Vsh.
     And thus, has arisen at last a metrologically correct way of definition of speed Vsh. And the formula (1) has the next kind now:

h=Vsh/f0          (1Т)

     Thus the physical sense of the shear waves consists in the following.
     The shear process is an imaginary part of a field of elastic fluctuations. And at result there were understandable some effects are observed at seismic prospecting. In particular, extremely low attenuation of elastic waves at their spreading along geological structures. Here the remarkable analogy to an electromagnetic field turns outЕ
     The electromagnetic field is characterized by real and imaginary components. The real part is responsible for active losses - heating, mechanical work. The imaginary part is responsible for spreading of a field. Attenuation of this (imaginary) part of a field is very unsignificant.
     It is known, for example, that wireless enthusiasts with the help the one-watt transmitter communicate on as much as possible distances, till to opposite points of the Earth.
     Precisely as occurs and at spreading of elastic waves. Seismic signal (it always has image of fading harmonious process) is formed by imaginary part of field (by shear waves), and attenuation of this waves is rather unsignificant. That is all seismic signals, are accepted various seismographs at seismic prospecting, are generated by imaginary, shear waves.
     But if the elastic wave arising as a result of shock influence is spread not in all directions, but only along rocky layers the echo-signal comes not from depth reflections of an elastic wave but from border of a rocky layer.
     Once again we shall note, that in result of shock influence (at seismic prospecting) the initial pulse is not spread in all directions. The own fluctuations which have arisen in each, separate, in elementary case, horizontal geological structure are spread under laws of geometrical optics, but only within the limits of these geological structures-resonators, in a horizontal direction. And when at realization seismic works they speak that the echo-signal is received from any depth, not so. The received signal is really an echo-signal, but from vertical border of that parallel-sided geological structure in which the given, concrete oscillatory process has arisen.
     It can be checked up very simply. If displacement of seismic cable to any side lead to temporal changes of the moment of arrival of an echo-signal for a while, proportional to this displacement, that, obviously, it is necessary to come to a conclusion that the echo-signal comes not from depth, but from some side. But if the echo-signal comes not from below, but from sides it becomes clear why seismic cut never corresponds to a real geological cut.
     As a result of representation of a field of elastic fluctuations as sum of real and imaginary components and the revealings of that fact, that in terrestrial thickness are spread the own elastic processes generated by an imaginary component of this field, it is possible to see very deep analogy between acoustics and electrodynamics. When on replacement the electrical of a direct current electrodynamics came and the electrical of a direct current has come as its rather insignificant part of electrodynamics. Also and generally accepted acoustics with its only mechanism - an interference - is included as a particular and little part into complex acoustics what is spectral acoustics (naturally, and spectral seismic prospecting).
     According to known fundamental positions of methodology of development of scientific knowledge, the research method based on new physical effect, becomes a source of essentially new information. It has taken place with a method spectral-seismic profilings (SSP). And as in a basis of a method SSP there was not one, and some new physical effects and the phenomena, this method is a source of a plenty of essentially new information.
     The borders revealed by a method SSP, are surfaces, on which may be mutual sliding of adjoining rock, and also microcracks and the zones with increased microcracking.
     Such borders share rock of a sedimentary cover. From the point of view of traditional seismic prospecting, between breeds with identical magnitude of density and of sound speed acoustic border is absent. With the help of spectral seismic prospecting it is borders are seen reliably. From positions of traditional seismic prospecting terrestrial thickness is sum of reflection borders but actually, and also from a position of spectral seismic prospecting, terrestrial thickness is sum of resonators, each of which - parallel-sided geological structure.
     Similar sort of border and objects was not revealed by any other research methods, and as result, method SSP is source of essentially new geological information. Method SSP allowes to reveal zones of tectonic dislocation.
     It is necessary to note, tectonic dislocations, descriptions of which are present at all geological and geophysical textbooks, actually, earlier were not researched. For this purpose there were no means. In the result, the properties of zones of tectonic dislocations described in textbooks are contrary to facts absolutely. So, according to the prevalent opinion, if the thickness of a sedimentary cover exceeds hundred meter, tectonic dislocations in crystal rock do not impact engineering constructions. However appeared, that it not so. Influence on engineering constructions on the part of tectonic dislocations with increase of thickness of a sedimentary cover does not decrease.
     Properties of rocks in zones of tectonic dislocations are so unexpected, and influence of these zones is so huge on many sides of our life that the bases of mountain sciences and building sciences will be in due course certainly reconsidered, so and geoecologies sciences and hydrogeology. The matter is that, as appeared, rocks in zones of tectonic dislocations, strictly speaking, are not solid materials. It, as though, solid liquids. Being in a condition increased microcracking on all thickness of a sedimentary cover, sedimentary breeds in zones of tectonic infringements have the lowered bearing capacity and the increased penetrability. Besides as appeared, in zones of tectonic dislocation there are pulsations with amplitude up to 10 see. In view of this effect it becomes clear, why, for example, pipes not simply sag in zones of tectonic dislocation, but are burst. Naturally, it will be, if they constantly pulsate and work on fatigue.
     Soil bearing capacity in zones of tectonic dislocation not simply has the lowered value, but this value it decreases after the beginning of construction work. In result, the house, erected in conditions of a strong ground, with time starts to collapse because the part of its base starts to sink into a ground.
     The increased penetration of rock in zones of tectonic dislocations , on the one hand, has the consequence that at drilling supply well there can be received a water. On the other hand, these zones are characterized by the increased egress of abyssal gases and it forms geopathogenic zones. As the statistics shows, residing at geopathogenic zones essentially increases probability of heavy diseases and reduces longevity. And, at last, if in a zone of tectonic dislocation there is burial place of toxic substances, loss of impermeability of these repository and, in result, penetration of these substances on the big depths and distances is inevitable.
     The tectonic dislocations in planetary scale are analogues of our circulatory system. They are as channels where liquid and gaseous substances on all planet are spread. And sedimentary rocks above tectonic dislocation connect (due to the increased penetrability of sedimentary rocks in these zones) tectonic dislocation with a ground surface. Cases when the buried substance is shown on very big distances from depository are known. Now, when we know about properties of rocks in zones of tectonic dislocations, the physics of this phenomenon became clear.
     Besides zones of tectonic dislocation are characterized by the increased values of quality of seismic signal. In other words seismic signal very long not fading sinusoid can look like. Consequently at presence of vibrating influence in these zones there can be resonant phenomena and as consequence, so-called rock bump or man-caused earthquakes.
     Cases of sudden destructions of pumping stations, tracks, forge shops, power stations, thermal power station are known... All these destructions occur quickly and objects submerge into a ground by pushes. One of such cases - the Chernobyl atomic power station. When it was destruction of 4-th block CHAES in 1986, seismologists registered two pushes, disputes about their origin are continued till now. Additional confirmation of that 4-th block CHAES is in a zone of a fracture, that the sarcophagus erected above it, steadily submerges into a ground is.
     Foundations of spectral seismic prospecting have arisen about a quarter of century back, and to present time this kind of geophysics has reached a level of an independent and reliable method for receiving of the important geological and engineering-geological information. Moreover, the information received with the help of this method is key for forecasting of man-caused accidents that is very in time, taking into account growing their probability and a condition of ecology.

LITERATURE

  1. Glikman A. "‘изика и практика спектральной сейсморазведки" на веб-сайте www.newgeophys.spb.ru

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