Search

In this paper is elaborated the usage and application of the seismic methods applied for geologically examined and relatively known environments, in order to determine their precision and efficiency. The seismic methods are used for researching the geological structure under the surface of the examined area, by determining the traveling speeds of the elastic waves through the different geological structures. Because of the horizontally layered geological structure (without presence of vertical faults) of the examined environment, as well as the adequate geo - mechanical characteristics of the geological environments (each deeper layer has higher speed of propagation of the elastic waves than the upper one) in this paper is elaborated the procedure of applying and interpretation of the refractive seismic method. The examined geological environment is presented as one profile line composed from two exploratory boreholes with a total length of 60m. The length of the refractive profiles, their number as well as the way of overlapping on the examined area depends of the geological structure, the depth of examination as well as the geo - mechanical characteristics. The depth of examination depends on the distance between the source and the receptor of the elastic waves and equals to one half of that length. The investigated area is examined with maximal depth of 30m, therefore the length of the refractive profiles reaches value of 60m. A total of four refractive profiles are made in order to cover the full length of the investigated area. The refractive profiles are overlapping on every 3Л of their length on the investigated area. The geo - mechanical characteristics of the geological structures are obtained with laboratory trials and through them for each geological structure is determined the speed of propagation of P and S elastic waves. Due to a lack of field trials the refractive profiles are made synthetically based on the geological and geo - mechanical data. Through the process of interpretation on the refractive profiles is determined the number of different geological structures, the speed of propagation of the elastic waves, and with the t0 method the depth to each boundary surface that separates two geologically different environments. [ABSTRACT FROM AUTHOR]

In order to obtain more concrete and more accurate results when the modelling of the under surface structure of the investigated area is made with the usage of geophysical examinations, if the field conditions allow it is necessary to be applied more than one geophysical method. In this paper is elaborated the procedure of complex interpretation of a seismic and geo - electrical model. The seismic model is modelling the geological structure by determining the speeds of propagation of the elastic waves which depends from the geo - mechanical characteristics of the geological environments. The geo - electrical model is modelling the investigated area by registering the changes on the electrical field which depends from the conductivity of the geological environments. The parameters of the investigated area (the layers of different geological environments, their electrical conductivity and geo - mechanical characteristics as well as the depth of examination) that is elaborated in this paper provide acceptable conditions for applying the refractive seismic method and the method of geo - electrical sounding. The refractive models as well as the models of geo - electrical sounding are made synthetically while using the data obtained from geological and geo - mechanical examinations. With the interpretation of the refractive models are determined the different geological environments (by the different speeds of propagation of the elastic waves) as well as the boundary surfaces that separates them, whereas with the interpretation of the models of apparent electrical resistivity the different geological structures and the boundary surfaces between them are defined by their actual specific electrical resistance. As a final phase of the modelling in the paper is made correlation between the two models (seismic refraction and geo - electrical sounding) as well as comparison and interpolation between the interpreted results in order to obtain more concrete and more precise vision for the under surface structure of the investigated area. [ABSTRACT FROM AUTHOR]

The seismic methods are based on registration and determination of the velocity of propagation of the elastic waves through geological known environments with the main difference in the rays that are registering. In the paper is elaborated the usage and effectiveness of the reflective method that is based on registering the elastic waves that are reflected from the boundary surface. Through the propagation velocities are identified the different geological structures, whereas the depth to each boundary surface through the t0 method. The investigated area that is chosen to be modelled through models of refraction and reflection is geologically investigated with five exploratory boreholes and has a total length of 210m. With the method of reflection the investigated area is examined to a maximal depth of 30m. Because the depth of examination of the environment, depends on the distance between the source and the receiver of the elastic waves and it's equal to one half of that length, the reflective profiles are made with length of 1 2 0 m, with the source of the elastic waves positioned in the middle of the measuring dispositive. In order to examine the whole length of the investigated area through the modelling a total of four reflective profiles are made. The modelling of the profiles is made synthetically on the basis of the geo - mechanical data for the geological environments as well as the geological data obtained from the exploratory boreholes. The modeling is obtained through direct and separate interpretation of the obtained seismic models. The seismic model of the investigated area is made through a process of complex interpretation of the data from the reflective models. [ABSTRACT FROM AUTHOR]