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Abstract

Data are presented from integrated special experiments which have been performed in conjunction with a seismic 30 reflection survey within the framework of IS089 ( Integrated Sei smi cs Oberpfal z 1989) coordinated by DEKOR(PG erman Continental Seismic Reflection Program) between July and Novembero f 1989. The main objective was to study the nature of P- and S-wave reflections and velocities, the Poisson's ratio and the seismic anisotropy in a medium of crystalline rocks around the KTB site (Continental Deep Drilling Program), where the borehole has reached a depth of 4000 m. A digital 5-unit geophone chain with 25 m spacing and three components was used for downhole recording. The program described here consists of: 1) shearwave 2D reflection profiling (SCMPw} ith two 10-12 km long lines crossing the KTB-site, source: 2 horizontal vibrators with different orientations, 3-component recording; 2) shearwave moving source profiling (S-MSP); downhole recording of the source points of the SCMP; 3) vertical seismic profiling (VSP) down to 3660 m with different source azimuths and offsets (zero-offset, 4 km, 8 km); P- and S-wave sources: explosives, horizontal and vertical vibrators, and horizontal hammer techniques. 4) multiple azimuth shearwave experiment (MASE) with 4 km and 8 km offset and horizontal vibrator sources (radial and transversal orientation). The VSP surveys display steeply dipping reflections, increasing in number below 3000 m depth. Horizontal structures, preferentially seen in the surface profiling, are the exception. Polarization analysis of shearwaves shows dominant azimuths in shearwave splitting which correlate with maximum horizontal stress (N 158° E) and with azimuth and dip of foliation.