Scholarly record

SPATIAL DIFFERENTIATION OF TECTONIC ACTIVITY OF REGIONAL AND LINEAR STRUCTURES TAKING INTO ACCOUNT CONTINUOUS INTERACTION OF ENDOGENIC AND EXOGENIC PROCESSES

N. Kiselev, N. Djachenko

Abstract

At present one has quite a good knowledge of lithospheric plate movement that occurs along such large living fractures as San Andreas in California, North Anatolian in Turkey and others. At the rest of the earth’s territory rock mass for the most part seem to be a static and motionless medium. However, as investigations show, even at small rock mass areas deformation processes of different period and amplitude take place. Such processes that occur in the earth’s crust are connected with a serious risk for objects, which came to be in affected zone of moving tectonic structures. Adversely affected are lengthy objects such as oil-trunk pipelines, underground manifolds and the like. Regional and local tectonic structures prove themselves as local faults in sedimentary cover. They manifest themselves on the surface as landscape lineaments within which increased fissuring and permeability become apparent and one can observe magnetic field and gamma background anomalies, increased radon concentration and its decomposition products in the surface air. Close correlation between basement and cover deformations lies in a differential displacement of the basement blocks, which in turn are one of the links in the mechanism to form folds and tectonic dislocations in sedimentary rock mass forming block-type hierarchy of different order. Combination of steady compression and tension conditions (applicable to the Donets Basin) results in activation of the block geotectonic conditions. In existing conditions tectonic blocks occupy an energy-efficient position. Especially this can be attributed to blocks of truncated pyramid shape, directed to the surface by their truncated edge, for which persistent sinking is typical. Investigations made at the Donbass geophysical testing area have shown that horizontal movement velocities (Donetsk-Makeevka area of the Donets Basin) were estimated as 0.01- 0.02 m/a year while vertical movements were on average 0.004 m/a year and only separate tectonic blocks were subjected to movements of the velocity 0.010-0.015 m/a year. Width of the identified geodynamic structures varies in the range of 100-500 meters; the strong manifestation of the dynamics of deformation processes takes palace as a rule within the interblock part. Among the problems that attract attention of research workers at present the most urgent one remains a problem of spatial differentiation of tectonic activity of regional and local linear structures taking into account continuous interaction of endogenic and exogenic processes. For the identification of dynamically stressed block-structure zones, zoning and mapping of them it is proposed to integrate methods of satellite geodesy with methods of dynamic geophysics. Long-term impact of stresses on rock mass result in the origination of additional deformation effects (layer-by-layer movements, formation of microcrack network, small bends and folds), which are in different states – from neutral one (already created tectonic fault) to a state close to instability. Having accumulated tectonic energy within morphological inhomogeneities of rock mass, these effects can lead to disastrous deformations of objects that are in the zone of their influence. Study and analysis of present-day short-term surface movements (present-day block movements) are made experimentally using Global Position System (GPS) and laying highaccuracy level lines by bench marks of an observation station. For the purpose of identifying indicators of deformation effects at the survey area gravity and magnetic fields are analyzed. Combining these indicators into linear zones allow determining regularities of location of such zones in space and time. Modern computer processing techniques use as formal descriptors actual physical characteristics of the process under consideration (surface subsidence and movement, change in lengths between observation points in time, ground surface absolute marks and so on) and estimating the character of manifestation of geodynamic processes in the form of dependence of aggregated characteristics of their manifestations on the surface.

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