Perpustakaan Digital ITB

Themultichannel surface-wavemethod is a current method used in geotechnical and environmental engineering to estimate the near surface shear-wave (S–wave) velocity profile. This non-invasive technique is based on the dispersive characteristic of surface waves, typically Rayleigh waves, whose dispersion curves can be obtained from dispersion images like the wavefield f-k power spectra. Herein an efficient methodology for multilayout and multichannel surface-wave data processing is proposed. This consists on stacking the recorded wavefields resultant from several acquisition layouts on the f-k domain: shot repetitions at the same position, shots at different offsets, direct and reverse shots, and also shots generated by different sources. The use of diverse acquisition layouts allows different investigations of the site and can lead to different frequencies and propagation modes to be excited. The stacking of these corresponding f-k spectra provides a f-k sum spectrum with higher signal-to-noise ratio which will improve the resolution of the phase velocity dispersion curves picked fromthat, for a larger frequency range. Consequently additional constraints will be available to invert the dispersion curves resulting in more realistic models. Real data applications, like the ones here presented, have demonstrated that the proposed methodology is effective in increasing the dispersion curves resolution and accuracy for a wider frequency range, with significant improvements for low frequencies (below 15 Hz).