For The Objects Which Are Geologically Dangerous.
Geodynamics as a factor of accidents risk
for the objects which are geologically dangerous.
The perspectives of prognostication
V. Jaroshenko1, I. Gladkikh2, B. Kapochkin3
1OAS "Odessagas"
2State Maritime Academy of Odessa, Ukraine
3Hydrometeorological Institute of Odessa, Ukraine
Coasts of seas and oceans are one of the most industrially developed territories. Placing in those territories the industrial objects, which are ecologically dangerous inevitably, results in emergency situations, which in their turn cause ecological consequences. One of the possibilities to minimize those consequences (ecological as well) is to forecast the accident-rate as well as prognosis of the emergency situations by stages starting from long-term to instant ones. Development of engineering and neogeodynamic approach promotes to employ the methods of diagnosis and prognosis concerning the technogenious accidents of geodynamic origin.
Study of geodynamic motions is one of the most important sections of geodesy. In civil engineering where the achievements of geodesic science are applied to practice, for the last few years has rapidly grown up the urgency to widely use the engineering-neogeodynamic approach. This approach is connected with regards for neogeodynamics when it is necessary to survey the building sites and maintenance of industrial, hydrotechnical and other constructions. The main task of engineering-neogeodynamic analysis is defined by the necessity of combined study of the dynamics of endogenic, exogenic and naturally technogeneous processes in complex which in its turn determines the character of territory preparation, operation qualities and possible changes of geological environment. Under engineering-neogeodynamic researches its peculiar place is taken by the assessment of possible seismic danger and geodynamic risk of the territory. In this concern it is important: to specify the place and parameters of active fractures and the points of their intersection; to state the mechanism of paleoseismodislocation spreading; to analyze the origin of motions by juxtaposition of amplitude charts and speed charts of the modern
quaternary and modern tectonic motions; to assess the tension of the Earth’s crust in the region of construction and its variations in time and space etc. Conducting such analysis we can distinguish zones of reconstruction\’s having neotectonic nature, high gradient neotectonic zones, places of high neotectonic divisibility of the territory, influence zones of neotectonically active fractures etc. Neogeodynamic researches are the necessary section of works that assess the growth of seismic intensity and analyze the territories from the point of view of its fitness for construction.
Designing, construction and maintenance of structures and communication nets are done generally ignoring the depth structure of sedimentary cover and crystallic width of the Earth’s crust. It is supposed that geological risk is stipulated only by the complex engineering-geological and hydrogeological situations, as well as by the intensive technogeneous load on the upper (0-50 m) layer of the geological environment. Thus, not only exogenic, but also endogenic processes in the Earth’s crust will influence the quality of construction if we consider this from the point of view of modern ideas about activity of the Earth’s crust in whole (from the Earth’s surface to the processes in the Earth mantle). In other words it can be said that destruction of structures and communication nets is possible on account of present motions along the breakdowns both in sedimentary and crystallic sections of the Earth’s crust.
The present research deals with the study of geodeformating processes of different temporal period with the view of their influence on the destruction of objects that are of certain ecological danger, such as gaspipelines.
Purpose of the work is to state cause and effect connections between character and peculiarities of geodynamic geodeformating motions and distracting processes of gaspipelines, to diagnose and prognosticate the periodical growths of accidents number by the way of observing the development of geodeformating processes. The present research is aimed to improve the approaches and methods of neogeodynamic analysis for practical purposes, and to make the guiding principles of engineering-neogeodynamic analysis including making of specialized cartographic material.
To achieve the goal it is necessary to resolve the following tasks:
1. To work out the criteria for distinguishing the accidents which are caused by geodeformating processes.
2. To state the peculiarities of the destructive process on the gaspipelines in time along with distinguishing latent cycles, which are characteristic of, wave deformation processes.
3. To state the dependence between gaspipelines fractures and seismic effects those reflect nonelastic character of geodeformating processes.
4. To state the dependence between the intensity of vertical motions and fractures of linear gaspipelines.
5. To state the dependence between the character of geodynamic motions and fractures of ground gaspipeline lines, fractures of underground gaspipelines, processes of building destruction.
6. To establish the statistic symptoms that can prognosticate activation of geodynamic motions.
7. To create the base for diagnosis and prognosis the growth periods for the accident-rate of gaspipelines.
The researches were conducted from 1995 to 1999. The basis of the research - database about the time and place of gasnets accidents given by “Odessagas” company, complex data which characterize the geodynamic condition of the territory, world and regional catalogues of earthquakes, data (both instrumental and bookish) of geothermal observations, instrumental data of depth gauge observations, observation data of regional hydrogeodeformating field (both instrumental and bookish), which are supplemented by confirming information about intensive geodynamic motions – registered data of time when construction collapse on the territory of the city.
Modern theoretical basis of quickly changing deformation field of the Earth’s surface was founded in the beginning of 70ies and registered as a scientific discovery (Vartanyan-Kulikov effect). There is a technology of hydrogeodeformating monitoring as a basis to disclose the structure of quickly changing regional deformation field. A lot of scientist mentions quick changes in the tense state of the Earth’s crust between the fractures of diagonal and orthogonal systems.
At present geodynamic motions of nonseismic character and fractures connected with them are subdivided into small amplitude and non-amplitude (of reciprocating character). Due to the use of whole deformographes it was established that in some places the deformed state of the Earth’s crust changes very quickly. The changes may be like a jump of deformations, which last several minutes or more prolonged deformation processes that may last from several hours to two days.
When the matter of geodynamic monitoring is concerned, first of all the question about temporal period of deformations arises. It is known that as a result of earthquakes the continuity of geological environment is damaged. Thus, the amplitude of abrupt vertical and horizontal shifts is measured by meters. Small-amplitude shifts have the integral scale of deformations not more than several centimeters a year. It is more complicated to evaluate the space-scale of non- amplitude (reciprocal) deformations, that show themselves only on the borders of the Earth’s crust blocks and cannot be surely discovered my standard leveling because of their short duration.
Nature of such deformation seems to me connected with tensions in the Earth’s crust, that in their turn are caused by dynamic processes with different space and time scales such as: short periodical changes of form and dimensions of the Earth, for example tides in the solid body of the Earth, spreading of the ocean floor in the spreading zones. There is evidence also about the variations of rotation speed of the Earth within twenty-four hours. The present research is based on the data of time chageability of the gas-tight violation in the thick net of gaspipelines covering the territory of Odessa and reflecting the process of tension changes in the deformed state of the Earth’s crust.
As a result of conducted works it was established that:
1.Accidents of constructions and gaspipelines are subject to extensive influence of geodynamic processes.
2.In the month scale of changeability the most essential is the influence of geodynamic processes (tides in the solid body of the Earth, rotational effects) with periods of 7 and 14,5 days with predominance of the week cycle.
3.In the annual scale the growth in the accident-rate of the gaspipelines is caused by the long gravitational waves. Judging from various data, which are corroborated by the observations after the accidents of the gaspipelines, deformations of such kind occur episodically in spring and autumn.
4.In the scale of several years the growth in accident-rate is unfluenced by the rotational effects.
5.It is established, that the rapid growth of gaspipeline accidents since 1995-1996, which coincided with the decrease in rotational speed of the Earth, increase of the Earth’s dimensions and the possible drop of tectonic tensions between blocks might cause the active deformation phenomena of wave origin within different time scale.
6.It is established, that from 1995 to 1997 the interannual changeability of geodynamic processes which is reflected in the peculiarities of accidents, was active in May and in the following years it was in October-November.
7.The study of phase shifts in spreading of wave geodeformating processes allows us to presume that in periods of episodically growth of tectonic tensions in the Earth’s crust, that are reffected by the non-plastic deformations (earthquakes) occurs temporal suppression of geodynamic deformations of wave nature (the level of accident-rate on the urban gaspipelines decreases). As for the phase shifts from the spreading of waves, it may be presumed the existence of essential changes in waweconductive characteristic of the Earth’s crust in those periods.
8.It is established that starting from 1995-96 in the activation period of geodeformating processes, especially in the conditions of high regional compression, which is characteristics by seismically, amplitudes of vertical reciprocal interblock shifts may reach 10-50 sm. within 3-5 days. Other types of deformations are also active.
9.It is established that the aerial gaspipelines (unlike underground gaspipelines and surface constructions) are damaged generally by the influence of plastic geodeformating processes of wave nature and hardly any subject to the influence of any seismic concussions.
10.As a result of conducted researches special calculation showed extremely high effectiveness of long-term prognoses in the growth of gaspipeline accidents. The prognoses are carried out with regard for existing monthly cycles of the accident-rate having geodynamic nature.
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