Transformation of four-component vertical seismic profiling records from Kola superdeep borehole, Russia

Abstract

Multicomponent vertical seismic profiling (VSP) provides valuable and reliable information about the geologic structure of the subsurface and is one of the best ways to study seismic anisotropy. However, some VSP tools have no orientation instrumentation, and additional preprocessing steps may be required. Using the example of the 1992 VSP survey on the Kola Superdeep Borehole, Russia, we describe a general approach to the data reduction for a VSP tool with any number of channels. Due to data redundancy provided by the four-component Kola VSP tool, we are able to increase signal-to-noise ratio, estimate coupling variations, perform geophone gain corrections, and carry out an additional quality control. We describe the computer implementation of the method based on the seismic processing system currently being developed. The program is able to apply tool-rotation correction based on the polarization properties of the first break. This rotation technique works well in the case of offset VSPs; whereas for zero-offset VSPs, we recommend more robust rotation procedure based on the use of the direct shear wave. We find that plotting of instantaneous polarization azimuths provides a useful device to control the performance of tool-correction approaches.