Parallel inversion of refracted travel times of P and SH waves using a function approximation

The paper discusses a possibility to determine refracting horizons and layer velocities with an inversion method. The basic idea for this method is that the lateral changes both in layer thicknesses and wave propagation velocities in the media are described by a series expansion using adequately chosen basic functions. Coefficients of the functions are calculated (estimated) with a qualified LSQ inversion. The advantage of this method is that it can be used in such case where both the thicknesses and velocities vary laterally continuously and slowly), and a solution can also be obtained when no continuous travel time curve was measured - mainly in multilayer cases - for each layer. This paper shows a possibility to use this inversion method for compressional and polarized shear waves measured independently but parallel at the same profile. The longitudinal and the transversal wave velocities are independent physical parameters of the underground from each other. Knowing the distributions of both velocities in near surface structures, it is possible to compute the Poisson ratio, which is important information for solving geotechnical and environmental tasks. The paper shows the results of a field experiment