The Multi-channel Analysis of Surface Waves (MASW) is a seismic method used to evaluate the shear-wave velocities of subsurface materials through the analysis of the dispersion properties of Rayleigh surface waves. The data are collected on the surface without the need of boreholes. A number of sensors is placed on the ground and they record the vibrations generated by seismic sources (active or passive).
The MASW seismic method allows to obtain the shear wave velocity (Vs) distribution in the ground and bedrock. It can be applied as a 1D sounding or as 2D profiles.
The MASW method exploits the dispersive nature of the ground. Each frequency component of the surface wave has a different propagation velocity (phase velocity). During the processing of the seismic data, dispersion curves are extracted from the data for each shot point (record). The dispersion curves show the phase velocity of the surface waves as a function of frequency. 1-D profiles of the shear wave velocity (Vs) versus depth can then be back calculated from the dispersion curve. A series of 1-D shear wave velocity profiles can be combined to produce a 2-D cross-section of the shear wave velocities along the seismic line.
The use of multicomponent data and the joint inversion of the Full Velocity Spectrum (instead of relying solely on the dispersion curve extraction) greatly improves the obtained seismic models.