Dispersion accuracy using Slant Stack transformation

Last decencies show the increasing interest in using Multichannel Spectral Analysis of Surface Waves (MASW) for ground structure recovery. Using MASW the dispersion characteristics of surface wave field is often determined using so called p−τ transformation known as Slant Stack (SL). It is commonly assumed that the acquisition geometry can affect the dispersion results and several general rules in current MASW practice are observed when this geometry is designed. They suggest for example to observe the minimum offset in order to avoid the interferences of surface waves with the body waves, the maximum offset in order to reach the required depth and maximum geophone spacing in order to avoid spatial aliasing. In the same time there are few reports on the influence of the array geometry on the resolution (i.e. accuracy) who deal with the array involved uncertainty of a dispersion curve. This paper aims a more detailed assessment of above problem: The accuracy of the SL procedure is studied as the function of the acquisition system like receiver spacing, receiver number, aperture length, sampling rate and signal frequency. It is shown how the not adequate array geometry design can corrupt the dispersion result and lead to erroneous interpretation. The easy to use criteria are formulated.