Application of the modified algorithms of fan filtering

The main problem in seismic prospecting is the so-called inverse problem-determination of the environment physical parameters based on the results of the registered waves observation. Because the waves registered by the method of vertical seismic profiling (VSP) have different natures of initiation, the VSP data are differed by the intensive interference of incident, reflected and other waves. This problem is addressed with known program complexes for VSP data processing by means of standard procedures of fan filtering and fields subtraction. Fan filtering is considered to allow the division of the waves efficiently into incident (with positive apparent speed) and emerging ones (with negative apparent speed). Practical usage of fan filtering by means of recurrent algorithms, Z-conversion or the algorithms based on the compression operation, however, results often in essential suppression of low and medium frequencies. Hence, serious deformations are introduced into the dynamic characteristics of the analyzed waves. Results of investigations show that these problems can be solved partially or completely, using digital spectrum algorithms based on the continuity properties of bispectrum fields and the choice of the nonrectangular discretization network by the frequency and wave number. Algorithms developed based on these principles are called modified fan algorithms (MFA).