Comparison of Wavefield Transformation Techniques for MASW Data Processing: Fid-Bau Portal

Comparison of Wavefield Transformation Techniques for MASW Data Processing

Rahimi, Salman / Wood, Clinton M.

This study investigates the influence of different wavefield transformation techniques on the resolution of derived dispersion data from the multichannel analysis of surface waves (MASW). In this regard, the performance of the four common transformation techniques, including Frequency Domain Beamformer (FDBF), frequency–wavenumber (FK), phase shift (PS), and slant stack (τp), is examined for different subsurface and wavefield conditions. The four transformation techniques resulted in similar dispersion images for sites with a very deep impedance contrast (~>100 m) with an almost homogenous soil profile. On the other hand, for sites with a very shallow impedance contrast (~<20 m), it is observed that the PS method often produces very low-quality dispersion data (lacking a clear trend), whereas the other methods generate high-quality dispersion data. Additionally, the FDBF-cylindrical is observed to be the most advantageous method for mitigating near-field effects. For complex sites where multiple modes of propagation are resolved, the four transformation techniques are observed to have different sensitivities to higher modes. Therefore, a composite dispersion approach from the four transformation techniques is recommended for use at such sites to avoid mode misidentification, increase the reliability of the data, detect multiple modes, and enhance the final shear wave velocity profile from the inversion process.