Wpływ spękań na anizotropię prędkości fal sejsmicznych w wybranych masywach skalnych

Abstract

Fracturing of the Earth crust is one of common features which influence on physical properties of rock mass. Random system of cracks rarely exist in rocks, much more popular is ordered crack system. It can be connected with conditions in which rocks were formed or can be result of processes which took place in geological history of rock mass. Anisotropy of physical properties of rocks is the effect of privileged some directions, the anisotropy of seismic wave in particular. It is characterized by the wave velocity is smaller in direction perpendicular to crack plane than in parallel direction. The existence of relationship between anisotropy of seismic wave velocity and anisotropy of cracks is possible thanks to use of tensor calculus. It enable to take into consideration both geometry and fracture orientation by using crack tensor, which components depend on both of this factors. Tensor calculus can be also apply to describe the directional distribution of seismic velocity. Velocity tensors, determined on the basis of seismic velocity measurement, show seismic anisotropy and allow to calculate velocity in optionally chosen direction. In fractured rocks velocity tensors show relation with crack tensors. The aim of this paper was to study connection between the anisotropy of seismic wave velocity and fracturing in different rock types. The realized studies have important meaning for evaluation stability and quality of rock mass during building tunnels, dams or industrial objects. They allow also to determine deposit structure, which have large meaning for building activity, because only few deposits get high quality raw material, which are stone blocks. In hydrology recognition of crack systems permit to determination properties of reservoir rocks and ways of underground water flow. It is also possible to make use of recognized rock complex as industrial waste lagoon. The knowledge about processes of crack system development can be precursor of earthquakes. For reasons of large meaning of fracturing it is very important to determine crack parameters in inaccessible rocks for direct observations.