GEOSPECTRUM S.C. services

GeoSpectrum company offers wide range of geophysical services (engineering seismics, Ground Penetrating Radar, electrical resistivity, microgravimetry and electromagnetics), geological, geotechnical and environmental protection.

Refraction technique was the first major geophysical technique used for the exploration or deep oilbearing layers. Currently, it is widely used in detailed studies of shallow subsurface.

Multichannel Analysis of Surface Waves technique- in active MASW 1D/2D/3D and passive MAM/ReMi 1D versions, bases on seismic S-waves analysis included in dispersive Rayleigh waves. A characteristic feature of the Rayleigh wave is that it represents about 70% of the total elastic energy waves recorded during the measurement. S-wave, whose velocity and attenuation are directly dependent on the elastic properties and density of the soil is ~ 90% of the Rayleigh wave. The difference between the technique MASW and MAM/Remi relies on different types of elastic energy sources. For MASW such sources are: sledgehammer, weight-drop, while for the passive measurements MAM/REMI random vibrations from traffic, building works, etc. in the vicinity of the acquisition area are applied. Often they are generated artificially by tractors, trucks, diggers, bulldozers.

Refraction tomography bases on the classic seismic refraction studies. Classical refraction gives good results in the ground with relatively low variable structure and layers (which differ significantly in velocities of seismic waves). In contrast, tomography can localize more complex structures where seismic wave velocities change in different directions gradually. Such places are fault zones, areas of karst, voids. Refraction tomography uses `first breaks` of refraction P-waves. The result of refraction tomography is determining velocity field in the tested ground.

The principle of operation of GPR is generating and sending an electromagnetic wave into examined soil, rock or other material. This is done by transmitting antenna generates a signal of a specific frequency. Wave passed through the soil is refracted, reflected on the geotechnical borders, when encountering facilities, infrastructure or other inhomogeneities wave is dispersed, called diffraction. Both antennas are connected to the control unit, which manages the generation of the reflected wave and the digital recording. GPR signal is triggered by measuring device mounted on wheels. When moving along the profile control unit stores separate traces of signal, which create cross-section called radarograms.

GPR profiling technique, also called reflexive profiling, is the simplest technique for GPR. It involves analysis of the structure surveyed medium using separate sections, where the location is designed before start of the measurement. Theirs positions are adjusted directly during the GPR acquisition depending on the field`s conditions. Given the fact that during the georadar surveys signal dampens with depth increasing and clay minerals contribute to this phenomenon as well. As a result, the effectiveness of GPR strongly restrict silty clay grounds and saturation of soil water.

GPR mapping is an advanced method of interpretation, where in addition to the classical interpretation GPR profiling, performs an interpolated summary of the many georadar sections. This is very important to determine their geometry to replicate as closely as possible the actual location for each profile in the field. For this purpose it can be used a precision GPS receiver. Usually parallel profiles or mesh of profiles (transverse and longitudinal) are applied for more precise scanning of the medium. The distance between the parallel profiles or the mesh size is chosen individually according to each job.

Geophysical surveys, which use geoelectrical methods base on the variation of electrical parameters of the soil. To understand the phenomena in ground-rock medium, in which electric current flows, it must be realized that such substrate resists while electric current flows through it. According to Ohm`s Law, resistance R is directly proportional to applied voltage U and inversely proportional to current intensity I. Basic parameter which is calculated using geoelectrical methods is electrical resistivity of the soil. Therefore, geoelectrical methods are equated with electrical resistivity methods. Resistivity is the property of material and on its basis we are able to characterize the ground below the surface.

Geophysical studies using resistivity method are based on the determination of electrical resistance changes of the ground. These changes are natural (geological) or anthropogenic, and have a resistance different from the surrounding ground.