Journal of Geophysical Research107 (2002), 2180, doi:10.1029/2001JB000843.

The three-dimensional (3-D) reflection-seismic dataset ISO-89 3D was recorded near the deep borehole KTB in southeastern Germany. Reflections from the SE1 reflector and from the top of the Erbendorf body (EB) in the upper crystalline crust can be identified in 5-10 % of the single-shot sections. The reflectors have been first identified in previous studies of stacked and migrated seismic data. In this paper the velocity and density variations of these two structures are estimated in a new way using true amplitude single-shot (vibroseis) data. The method uses the direct wave Pg as a reference phase and models the amplitude ratios of the SE1 and EB reflections to Pg. Modeling in this paper uses a combination of ray theory and the reflectivity method, and the SE1 and the top of the EB are assumed to be obliquely oriented 1-D structures. Pg modeling shows that a depth-dependent velocity function within the uppermost crystalline basement explains the amplitudes and traveltimes of this phase with sufficient accuracy. The largest observed amplitude ratios SE1/Pg and EB/Pg are explained by laminated models with strong velocity contrasts and with reflection coefficients of magnitude 0.1-0.2 (SE1) and 0.05-0.15 (EB). The total thickness of the reflecting zones is less than ~300 m. Pg amplitude modeling requires low Qp factors (<100) to a depth of ~1km, whereas at larger depths, values of several hundred are necessary to keep the SE1 and EB velocity contrasts in realistic ranges. Both reflectors can be interpreted as cataclastic zones. For the SE1 this interpretation agrees with the view that it is a steeply dipping thrust fault which continues the tectonic Franconian Lineament into the upper crust. We assume that the EB is the fractured top of a high-velocity zone at depths below ~10 km, known from earlier wide-angle measurements. Both reflectors have large weakly reflecting or nonreflecting parts. The SE1 is nonreflecting at the intersection with the KTB borehole. The interaction of plane elastic waves with a plane boundary between two anisotropic elastic half-spaces is investigated. The anisotropy dealt with in this study is of a general type. Explicit expressions for energy-related reflection and transmission coefficients are derived. They represent an approximation which is valid for a small deviation of the elastic parameters from isotropy. Classical perturbation theory is applied on a 6x6 non-symmetric real eigenvalue problem to calculate first-order corrections for the polarization and stress of the plane waves. The explicit solution of the isotropic problem is used as a reference case. Degenerate perturbation theory is used to consider the splitting of the isotropic S-wave into two anisotropic qS-waves. The boundary conditions for two half-spaces in welded contact lead to a 6x6 system of linear equations. A correction to the isotropic solution is calculated by linearization. The resultant coefficients are functions of horizontal slowness, Lamé parameters and densities of the reference media, and of the perturbation of the elasticity tensors from isotropy.