A Comparison of Different Epikarst Settings Obtained Using Statistical Resistivity Models

The epikarst (the subsurface cavernous part of karstic rock studied in the Bakony Regions, the Mecsek Mountains and the area of Pádis) was compared across several karst sample sites. Since the degree of cavity formation in the epikarst cannot be studied directly, statistical analysis of the measured resistivity values was used to determine and compare the characteristics of the epikarst at different sample sites and, thus, the associated karst areas. For this, the significance of bedrock resistivity values obtained by Vertical Electrical Sounding (VES) was determined by t-tests. The mean values and standard deviations along the profiles of the VES measurement sites were calculated and graphically represented. It was established that the epikarst of profiles with high resistivity mean values is thicker, and the epikarst is of heterogeneous cavity formation (cavity formation is of different degrees) at sites where the standard deviation of resistivity is high. The epikarst of some karst sample sites can be compared by their standard deviation fields since in areas with higher resistivity, a thicker epikarst results in more expanded cavities and a lower water table, while heterogeneous cavity formation causes different cavity sizes and different resistivities. At sites where the standard deviation fields overlap with each other, their epikarsts are similar, at those where they do not overlap, they are different, and at sites where the fields touch, their similarity is transitional. If the standard deviation fields overlap each other, those with higher mean values and higher standard deviation have more cavities and their cavity formation is more heterogeneous. The epikarst with these characteristic features is regarded as more mature because at a lower water table, a higher arithmetic mean of resistivity and a higher standard deviation can be established. The reliability of the comparisons is shown by the fact that those with a more mature epikarst are karstified to a greater degree.