The application of geoelectrical attributes based on crossed square array resistivity sounding data at 'Pudarske Kolibe' site in eastern Serbia

Abstract

Most of modern geophysical investigations routinely utilize seismic exploration method. 3D seismic and multiple seismic attributes enable the most complete definition of the local geological setting. This paper deals with utilization of crossed-square geoelectrical sounding method, which can be used for a 3D interpretation of resistivity sounding data as well as for defining additional geoelectrical attributes. With crossed-square array, we get a directional independent measurement and multiple geoelectrical attributes (ρm, ρx, n, θ and ξ). A more complete approach towards better interpretation is achieved with maps of five attributes: geometric mean apparent resistivity (ρm), average apparent resistivity (ρx) apparent anisotropy coefficient (n), azimuth of the plane beddings (θ) and a ratio of deviation from homogeneous anisotropic subsurface model (ξ). Multiple geoelectrical attribute maps correspond to depth of investigation of the array, like time and depth slices in seismic method. Horizontal resolution and the depth of investigation are controlled by the size and position of the array. Vertical resolution is, however, limited just like for the usage of any other electrode array in geoelectrical sounding. Combination of depth maps and profile maps enables a 3D interpretation similar to 3D cubes in seismic and recent software enables 3D modelling. The measurements using crossed square array were conducted at site 'Pudarske kolibe' in Eastern Serbia. The goal was to determine and separate 3D calcarinte bodies created in the depositional process, but also the eventual existence of electrical anisotropy in fluvial and shallow see water sediments. Results of investigations revealed the existence of electrical anisotropy with apparent anisotropy coefficient (n) up to the value of 2 and, on the other hand, successfully delineated calcarenite bodies embedded in sedimentary formations present at investigated site.