Contribution of Simplified Surface Waveform Calculation to Separate Dispersion Curves in MASW

Abstract

Accurate picking of dispersion curves is the most critical stage in Multichannel Analysis of Surface Waves (MASW) method. Although there is several acquisition and numerical techniques for the optimal extraction, sometime, this requirement cannot be valid due to interference, which includes different modes, noises, and also lateral inhomogeneity in the near-surface earth. Hence, the interference between the different modes of surface waves can be so serious that neither fundamental, nor higher mode dispersion curve can be extracted with an accurate and a reliable. For this, we calculate surface waveforms, including geometrical and intrinsic dispersion, based on the summation of the particular seismic impulses corresponding to particular frequency-phase velocity curve points for geophone positions from the seismic source. This methodology is demonstrated by using both synthetic and real shot gathers. Synthetic calculations provide us a simple way to check accuracy of dispersion curve picking on a shot gather, which it is the fundamental or higher mode.