P wave material anisotropy of a tectono-metamorphic terrane: An active source seismic experiment at the KTB super-deep drill hole, southeast Germany

Abstract

An active-source seismic experiment at the KTB deep drill hole in southeast Germany reveals seismic P wave anisotropy to exist within a tectono-metamorphic sub-terrane of the crystalline Bohemian massif. The experiment used multi-azimuth vertical seismic profiling whereby downhole sensors recorded surface seismic Vibroseis sources located along six 7.5-km radial profiles emanating from the borehole location. Representative bulk anisotropic P wave velocities of the upper crust were derived from this seismic data and compared with predictions of velocity and anisotropy based on petrophysical laboratory measurements and geological information. We show that azimuth and inclination behavior of the observed anisotropy is consistent with characterization of the geology surrounding the borehole as a coherent regional block containing pervasive highly tilted foliation. This seismic anisotropy can be explained by "intrinsic" material properties associated with the well-developed foliation fabrics. Copyright 2004 by the American Geophysical Union.