P-Wave anisotropy of rocks from the seismic area in Western Bohemia

P-Wave velocity of metamorphic and magmatic rocks from the West Bohemian Saxothuringian (e.g. phyllites, quartzites, metabasites, mica schists, orthogneisses, granites and young volcanics) was measured using an acoustic method. The specimens were saturated with water in order to avoid the influence of open microcracks and porous space. Anisotropy coefficients were calculated from measurements in three perpendicular directions. Phycodes phyllitic slates as well as phyllites of the Frauenbach group from the region near the towns Luby and Kraslice exhibit relatively high VP up to 6800 m/s and extremely high anisotropy in the interval 25–49%. The lowest VP, under 4744 m/s, was found in light and phyllitic quartzites exhibiting, their anisotropy up to 29%. The high anisotropy of phyllites and quartzites is caused by an arrangement of phyllosilicates defining the metamorphic schistosity S2 and controlling directional changes of VP. In the case of mica-schists of the Svatava crystalline complex, significant roles may be played also by other foliations. The relatively lower anisotropy of mica-schists from the vicinity of the town of Olov? compared to that of phyllites is partly due to this feature, partly due to lesser amount of mafic minerals. The anisotropy found by laboratory measurements has helped to find the relation between the geological structure and elastic wave propagation in the seismic area under study.