ABSTRACT:

The present study concern carbonate rocks from south Poland. Measurements of seismic and electric anisotropy of the rock mass were done along radial profiles having common central point using 12- channels seismometer ABM Terralock Marc 6+ and resistivity meter ABM Terrameter SAS 300. Results of field measurements were interpreted to estimate components of velocity tensor and conductivity tensor in the site under study. It allowed to establish the relationship between characteristic parameters of the tensors. This knowledge allows to find out mean direction of cracks sets and consider about fracture saturation in sites where the rocks are inaccessible to direct observation.

1 INTRODUCTION

One of the most characteristic features of rocks is occurrence of cracks of different kind and size. This discontinuities have an important influence on physical properties of rocks. Preferred orientation of crack systems involves anisotropy of seismic wave velocity and anisotropy of rock resistivity. Cracks cause velocity reduction, which depends on crack geometry and elastic properties of material filling cracks (water, gas or silt). The flow of cracks on electric conductivity of rock is different. Depending on crack filling they can enlarge or reduce electric resistivity in comparison to uncracked solid. The study of relationships between crack and seismic or electric anisotropy allowed to use combined geophysical methods like seismic refraction method and multi-level electric profiling for determination of fracture density and orientation of crack systems and fracture filling as well. Earlier measurements were done for rocks without overburden (Idziak, Stan-Kleczek, 2006b). The result of this study showed that velocity of P-wave was maximum for wave propagating parallel to crack strike and minimum for wave propagating perpendicular to it. Anisotropy of seismic wave velocity decreased if crack saturation increased. Anisotropy of electrical properties of fractured rock was more complex and depended on a crack filling.

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