A Processing Technique for Three Component Seismic Data: Use of Polarisation Characteristics

Abstract

This paper presents a method that uses polarisation characteristics of three component seismic data (recorded by surface reflection profiling, VSP etc.) for discrimination and filtering of waves. Discrimination of waves in single (e.g., vertical) component data is based on frequency characteristics and apparent velocities, obtained from line-up observations. When three component records are used, discrimination based on polarisation characteristics is also possible. In this paper, we first describe the method by which polarisation characteristics are determined from three component records, and how these characteristics are used in polarisation filtering. Polarisation characteristics are estimated by eigenvector analysis of covariance matrices, which are obtained from three component data. The parameters thus obtained are then used in polarisation filtering. Following this is a discussion of the method. In this discussion, three component data, synthesized from waves having various polarisation characteristics, are used. Finally, we present an actual application of this method to data obtained in a surface observation. This example demonstrates that by the use of polarisation characteristics, it is possible to (1) discriminate linearly polarised waves (P or S waves) from elliptically polarised waves (Rayleigh type surface waves); and (2) distinguish between P waves and S waves, on the basis of differences in particle motion direction.