Dispersion interpretation from synthetic seismograms and multichannel analysis of surface waves (MASW)

Synthetic seismograms and multi-channel analysis of surface waves (MASW) enhance interpretations of a field site’s velocity characteristics. MASW layer models were numerically modeled to produce synthetic shot gathers. Iteratively updating the Pand S-wave synthetic velocity models created shot gathers with first-arrivals and Rayleighwave dispersion that closely matched field data. The resulting velocity models gave an estimation of the Vp:Vs ratio. Dispersion images generated from synthetic shot-gather subsets linked acquisition parameters to modal phenomena observed in initial processing of field data. Similar comparisons gave qualitative estimations of phase-velocity averaging over the spread-length for specific frequency bands. We suggest integrating modeling, using MASW Vs interval velocities, to differentiate between true velocity structure and transformation artifacts.